feat: Anhänge je Stunde, Klausur-Sitzplan mischen, Gefährdungsbeurteilungs-Assistent

Lesson bekommt dieselbe Anhang-Infrastruktur wie Documentation (Material,
Arbeitsblätter, Experimentunterlagen), samt Fix einer Sync-Lücke, die Anhang-
Dateibytes bisher nur für Documentation statt generisch übertragen hat
(IHasAttachments). Sitzplan-Tab bekommt einen "Plätze mischen"-Button für
Klausursitzpläne. Neu: mehrschrittiger Gefährdungsbeurteilungs-Assistent mit
optionalem KI-Entwurf (ai-backend/gbu.php) und PDF-Export, Format bewusst als
JSON-Anhang statt eigener Datenbank-Entität. Details und Architekturentscheidungen
in TODO.md (4.2, 7.1.5, 10.1.8).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

LehrerApp.Desktop/Services/AiPlanningService.cs

@@ -381,6 +381,47 @@ public class AiPlanningService(HttpClient http, ILessonRepository lessons,
         }
     }
 
+    /// <summary>
+    /// Fragt einen Entwurf für eine Gefährdungsbeurteilung zu genau dieser Lesson ab (Nutzerwunsch
+    /// neben 4.2 "Anhänge je Stunde"): die KI erkennt aus Thema/Verlaufsplan das Experiment und
+    /// liefert Stoffe, Gefährdungen, Schutzmaßnahmen etc. als Entwurf zur Weiterbearbeitung im
+    /// Gefährdungsbeurteilungs-Assistenten. Ändert nichts an der Lesson selbst.
+    /// </summary>
+    public async Task<AiHazardAssessmentResponse> RequestHazardAssessmentDraftAsync(Unit unit, AiLesson lesson, string token)
+    {
+        var request = new AiHazardAssessmentRequest { Unit = BuildContext(unit, ""), Lesson = lesson };
+
+        using var req = new HttpRequestMessage(HttpMethod.Post, "gbu.php")
+        {
+            Content = JsonContent.Create(request, options: JsonOptions),
+        };
+        req.Headers.Authorization = new("Bearer", token);
+
+        HttpResponseMessage resp;
+        try { resp = await http.SendAsync(req); }
+        catch (HttpRequestException)
+        {
+            throw new AiBackendException("Der KI-Dienst ist nicht erreichbar. Bitte Internetverbindung prüfen.");
+        }
+
+        if (resp.StatusCode == HttpStatusCode.Unauthorized)
+            throw new AiBackendException("Anmeldung abgelaufen. Bitte in den Einstellungen erneut anmelden.");
+        if (resp.StatusCode == (HttpStatusCode)402)
+            throw new AiBackendException("Nicht genügend KI-Guthaben. Bitte Guthaben aufladen.");
+        if (!resp.IsSuccessStatusCode)
+            throw new AiBackendException("Die Anfrage an den KI-Dienst ist fehlgeschlagen.");
+
+        try
+        {
+            var result = await resp.Content.ReadFromJsonAsync<AiHazardAssessmentResponse>(JsonOptions);
+            return result ?? throw new AiBackendException("Die Antwort der KI konnte nicht verarbeitet werden.");
+        }
+        catch (Exception ex) when (ex is not AiBackendException)
+        {
+            throw new AiBackendException("Die Antwort der KI konnte nicht verarbeitet werden. Bitte erneut versuchen.");
+        }
+    }
+
     /// <summary>
     /// Rein (nur Repository-Lesezugriff für den Alternativpfad-Katalog, kein Schreiben) — testbar
     /// mit Fakes. Gibt die zu speichernden Lesson-Objekte zurück; der Aufrufer ruft

LehrerApp.Desktop/Services/PdfExportService.cs

@@ -73,6 +73,23 @@ public sealed record DocumentationPrintEntry(
     bool IsConfidential,
     bool IsDraft);
 
+public sealed record HazardAssessmentPrintData(
+    string Title,
+    string GroupLabel,
+    string DateDisplay,
+    string KindLabel,
+    string Procedure,
+    IReadOnlyList<HazardSubstancePrintRow> Substances,
+    IReadOnlyList<string> Hazards,
+    IReadOnlyList<string> ProtectiveMeasures,
+    string FirstAid,
+    string Disposal,
+    string Notes,
+    bool IsAiAssisted);
+
+public sealed record HazardSubstancePrintRow(
+    string Name, string Amount, string Pictograms, string HStatements, string PStatements);
+
 /// <summary>
 /// PDF-Erzeugung über QuestPDF (11.3). Liefert fertige Bytes - der Speicherdialog läuft wie bei
 /// allen Exporten über <see cref="ExportService"/>. Lebt bewusst in LehrerApp.Desktop statt Core:
@@ -346,8 +363,95 @@ public sealed class PdfExportService
             page.Footer().Element(Footer);
         })).GeneratePdf();
 
+    public byte[] BuildHazardAssessmentPdf(HazardAssessmentPrintData data) =>
+        Document.Create(container => container.Page(page =>
+        {
+            page.Size(PageSizes.A4);
+            page.Margin(36);
+            page.DefaultTextStyle(style => style.FontSize(9));
+
+            page.Header().Element(header => Header(header, $"Gefährdungsbeurteilung · {data.Title}",
+                $"{data.GroupLabel} · {data.KindLabel} · {data.DateDisplay}"));
+
+            page.Content().PaddingVertical(10).Column(column =>
+            {
+                column.Spacing(10);
+                if (data.IsAiAssisted) column.Item().Element(AiDisclaimerBanner);
+                if (!string.IsNullOrWhiteSpace(data.Procedure))
+                    column.Item().Element(c => TextSection(c, "Durchführung", data.Procedure));
+                if (data.Substances.Count > 0)
+                    column.Item().Element(c => SubstanceTable(c, data.Substances));
+                if (data.Hazards.Count > 0)
+                    column.Item().Element(c => BulletSection(c, "Gefährdungen", data.Hazards));
+                if (data.ProtectiveMeasures.Count > 0)
+                    column.Item().Element(c => BulletSection(c, "Schutzmaßnahmen", data.ProtectiveMeasures));
+                if (!string.IsNullOrWhiteSpace(data.FirstAid))
+                    column.Item().Element(c => TextSection(c, "Erste Hilfe", data.FirstAid));
+                if (!string.IsNullOrWhiteSpace(data.Disposal))
+                    column.Item().Element(c => TextSection(c, "Entsorgung", data.Disposal));
+                if (!string.IsNullOrWhiteSpace(data.Notes))
+                    column.Item().Element(c => TextSection(c, "Weitere Hinweise", data.Notes));
+            });
+
+            page.Footer().Element(Footer);
+        })).GeneratePdf();
+
     // ── Bausteine ───────────────────────────────────────────────────────────────
 
+    private static void AiDisclaimerBanner(IContainer container) =>
+        container.Background(Colors.Orange.Lighten4).Padding(8).Text(
+            "⚠️ Enthält KI-generierte Anteile — kein rechtssicheres Dokument. Vor Verwendung " +
+            "eigenverantwortlich prüfen, insbesondere H-/P-Sätze und Mengenangaben gegen das " +
+            "Sicherheitsdatenblatt.").FontSize(9).FontColor(Colors.Orange.Darken3).SemiBold();
+
+    private static void TextSection(IContainer container, string title, string text) =>
+        container.Column(column =>
+        {
+            column.Item().Text(title).FontSize(11).SemiBold();
+            column.Item().Text(text);
+        });
+
+    private static void BulletSection(IContainer container, string title, IReadOnlyList<string> items) =>
+        container.Column(column =>
+        {
+            column.Item().Text(title).FontSize(11).SemiBold();
+            foreach (var item in items)
+                column.Item().Text($"• {item}");
+        });
+
+    private static void SubstanceTable(IContainer container, IReadOnlyList<HazardSubstancePrintRow> rows) =>
+        container.Column(column =>
+        {
+            column.Item().Text("Gefahrstoffe").FontSize(11).SemiBold();
+            column.Item().Table(table =>
+            {
+                table.ColumnsDefinition(columns =>
+                {
+                    columns.RelativeColumn(2f);
+                    columns.RelativeColumn(1f);
+                    columns.RelativeColumn(1.3f);
+                    columns.RelativeColumn(2f);
+                    columns.RelativeColumn(2f);
+                });
+                table.Header(header =>
+                {
+                    header.Cell().Element(HeaderCell).Text("Stoff").SemiBold();
+                    header.Cell().Element(HeaderCell).Text("Menge").SemiBold();
+                    header.Cell().Element(HeaderCell).Text("GHS").SemiBold();
+                    header.Cell().Element(HeaderCell).Text("H-Sätze").SemiBold();
+                    header.Cell().Element(HeaderCell).Text("P-Sätze").SemiBold();
+                });
+                foreach (var row in rows)
+                {
+                    table.Cell().Element(BodyCell).Text(row.Name);
+                    table.Cell().Element(BodyCell).Text(row.Amount);
+                    table.Cell().Element(BodyCell).Text(row.Pictograms);
+                    table.Cell().Element(BodyCell).Text(row.HStatements);
+                    table.Cell().Element(BodyCell).Text(row.PStatements);
+                }
+            });
+        });
+
     /// <summary>Horizontaler Balken, 0-100 % der verfügbaren Zellenbreite (max. 150pt).</summary>
     private static void Bar(IContainer container, double percent, string color) =>
         container.MaxWidth(150).Height(7).Background(Colors.Grey.Lighten3)

LehrerApp.Desktop/ViewModels/Groups/HazardAssessmentWizardViewModel.cs

@@ -0,0 +1,376 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using LehrerApp.Core.AiPlanning;
+using LehrerApp.Core.Models;
+using LehrerApp.Desktop.Services;
+using System.Collections.ObjectModel;
+using System.Globalization;
+
+namespace LehrerApp.Desktop.ViewModels.Groups;
+
+// ── Anzeige: Experimentart, GHS-Piktogramme (Nutzerwunsch neben 4.2 "Anhänge je Stunde") ────────
+
+public static class ExperimentKindDisplay
+{
+    public static string[] Options { get; } = ["Lehrerversuch", "Schülerversuch", "Demonstrationsversuch"];
+
+    public static string Label(ExperimentKind kind) => kind switch
+    {
+        ExperimentKind.Schuelerversuch => "Schülerversuch",
+        ExperimentKind.Demonstrationsversuch => "Demonstrationsversuch",
+        _ => "Lehrerversuch",
+    };
+
+    public static ExperimentKind FromLabel(string? label) => label switch
+    {
+        "Schülerversuch" => ExperimentKind.Schuelerversuch,
+        "Demonstrationsversuch" => ExperimentKind.Demonstrationsversuch,
+        _ => ExperimentKind.Lehrerversuch,
+    };
+
+    /// Für die KI-Antwort, die den unmarkierten Enum-Namen ("Schuelerversuch") statt der
+    /// deutschen Anzeige-Bezeichnung liefert (siehe ai-backend/gbu.php "Antwortformat").
+    public static ExperimentKind FromWireValue(string? value) =>
+        Enum.TryParse<ExperimentKind>(value, ignoreCase: true, out var kind) ? kind : ExperimentKind.Lehrerversuch;
+}
+
+public static class GhsPictogramDisplay
+{
+    private static readonly (GhsPictogram Value, string Code, string Label)[] All =
+    [
+        (GhsPictogram.Explosive, "GHS01", "Explosionsgefährlich"),
+        (GhsPictogram.Flammable, "GHS02", "Entzündbar"),
+        (GhsPictogram.Oxidizing, "GHS03", "Brandfördernd"),
+        (GhsPictogram.CompressedGas, "GHS04", "Gase unter Druck"),
+        (GhsPictogram.Corrosive, "GHS05", "Ätzend"),
+        (GhsPictogram.Toxic, "GHS06", "Giftig"),
+        (GhsPictogram.Harmful, "GHS07", "Gesundheitsschädlich/Reizend"),
+        (GhsPictogram.HealthHazard, "GHS08", "Gesundheitsgefährdend"),
+        (GhsPictogram.Environmental, "GHS09", "Umweltgefährdend"),
+    ];
+
+    public static string Code(GhsPictogram value) => All.First(o => o.Value == value).Code;
+    public static string Label(GhsPictogram value) => All.First(o => o.Value == value).Label;
+
+    public static GhsPictogram? FromCode(string? code)
+    {
+        if (string.IsNullOrWhiteSpace(code)) return null;
+        foreach (var option in All)
+            if (string.Equals(option.Code, code.Trim(), StringComparison.OrdinalIgnoreCase))
+                return option.Value;
+        return null;
+    }
+
+    public static List<GhsPictogramOption> BuildOptions(IEnumerable<GhsPictogram>? selected = null)
+    {
+        var selectedSet = (selected ?? []).ToHashSet();
+        return All.Select(o => new GhsPictogramOption(o.Value, $"{o.Code} · {o.Label}") { IsSelected = selectedSet.Contains(o.Value) }).ToList();
+    }
+}
+
+public partial class GhsPictogramOption(GhsPictogram value, string label) : ObservableObject
+{
+    public GhsPictogram Value { get; } = value;
+    public string Label { get; } = label;
+    [ObservableProperty] private bool _isSelected;
+}
+
+// ── Zeile im Gefahrstoff-Editor (Wizard-Schritt 2) ───────────────────────────────────────────────
+
+public partial class HazardSubstanceEditItem : ObservableObject
+{
+    [ObservableProperty] private string _name = "";
+    [ObservableProperty] private string _amount = "";
+    [ObservableProperty] private string _hStatements = "";
+    [ObservableProperty] private string _pStatements = "";
+    public ObservableCollection<GhsPictogramOption> PictogramOptions { get; }
+    public Action<HazardSubstanceEditItem>? OnRemove { get; set; }
+
+    public HazardSubstanceEditItem(HazardSubstance? source = null)
+    {
+        PictogramOptions = new ObservableCollection<GhsPictogramOption>(
+            GhsPictogramDisplay.BuildOptions(source?.GhsPictograms));
+        if (source is null) return;
+        Name = source.Name;
+        Amount = source.Amount;
+        HStatements = source.HStatements;
+        PStatements = source.PStatements;
+    }
+
+    [RelayCommand]
+    private void Remove() => OnRemove?.Invoke(this);
+
+    public HazardSubstance ToModel() => new()
+    {
+        Name = Name.Trim(),
+        Amount = Amount.Trim(),
+        HStatements = HStatements.Trim(),
+        PStatements = PStatements.Trim(),
+        GhsPictograms = PictogramOptions.Where(o => o.IsSelected).Select(o => o.Value).ToList(),
+    };
+}
+
+// ── Wizard: Gefährdungsbeurteilung anlegen/bearbeiten ────────────────────────────────────────────
+
+/// <summary>
+/// Mehrschrittiger Assistent für eine Gefährdungsbeurteilung zu einem Experiment (Nutzerwunsch
+/// neben 4.2 "Anhänge je Stunde"). Persistiert NICHT selbst — der Aufrufer (LessonDialog)
+/// serialisiert <see cref="Result"/> zu JSON und hängt es über die bestehende
+/// Anhang-Infrastruktur an die Lesson an (Dateiname endet auf ".gbu.json", siehe TODO.md 4.2).
+/// KI-Unterstützung ist optional: ohne <paramref name="ai"/>/<paramref name="unit"/>/
+/// <paramref name="lesson"/> bleibt <see cref="CanUseAi"/> false und der Assistent funktioniert
+/// rein manuell.
+/// </summary>
+public partial class HazardAssessmentWizardViewModel : ObservableObject
+{
+    private static readonly string[] StepTitlesArray =
+        ["Basisdaten", "Gefahrstoffe", "Gefährdungen & Schutzmaßnahmen", "Erste Hilfe & Entsorgung", "Zusammenfassung"];
+
+    private readonly AiPlanningService? _ai;
+    private readonly AiSettingsService? _aiSettings;
+    private readonly Unit? _unit;
+    private readonly Lesson? _lesson;
+
+    [ObservableProperty] private int _stepIndex;
+    [ObservableProperty] private string _title = "";
+    [ObservableProperty] private string _titleError = "";
+    [ObservableProperty] private string _groupLabel = "";
+    [ObservableProperty] private string _dateText = DateOnly.FromDateTime(DateTime.Today).ToString("dd.MM.yyyy");
+    [ObservableProperty] private string _kindName = ExperimentKindDisplay.Options[0];
+    [ObservableProperty] private string _procedure = "";
+
+    public ObservableCollection<HazardSubstanceEditItem> Substances { get; } = [];
+    public bool HasSubstances => Substances.Count > 0;
+
+    [ObservableProperty] private string _newHazard = "";
+    public ObservableCollection<string> Hazards { get; } = [];
+    [ObservableProperty] private string _newProtectiveMeasure = "";
+    public ObservableCollection<string> ProtectiveMeasures { get; } = [];
+
+    [ObservableProperty] private string _firstAid = "";
+    [ObservableProperty] private string _disposal = "";
+    [ObservableProperty] private string _notes = "";
+
+    [ObservableProperty] private bool _isAiAssisted;
+    [ObservableProperty] private bool _isAiBusy;
+    [ObservableProperty] private string _aiError = "";
+    public string AiButtonLabel => IsAiBusy ? "KI fragt..." : "🤖 KI-Entwurf erstellen";
+
+    public bool CanUseAi => _ai is not null && _aiSettings is { Enabled: true, IsLoggedIn: true }
+        && _unit is not null && _lesson is not null;
+
+    public string[] StepTitles => StepTitlesArray;
+    public string StepTitle => StepTitles[StepIndex];
+    public string StepProgressLabel => $"Schritt {StepIndex + 1} von {StepTitles.Length}";
+    public int StepCount => StepTitles.Length;
+    public bool IsFirstStep => StepIndex == 0;
+    public bool IsLastStep => StepIndex == StepTitles.Length - 1;
+    public bool IsBasicsStep => StepIndex == 0;
+    public bool IsSubstancesStep => StepIndex == 1;
+    public bool IsHazardsStep => StepIndex == 2;
+    public bool IsFirstAidStep => StepIndex == 3;
+    public bool IsSummaryStep => StepIndex == 4;
+    public string[] KindOptions => ExperimentKindDisplay.Options;
+    public string DialogTitle => _editing ? "Gefährdungsbeurteilung bearbeiten" : "Gefährdungsbeurteilung erstellen";
+
+    private readonly bool _editing;
+
+    public HazardAssessment? Result { get; private set; }
+
+    public HazardAssessmentWizardViewModel(HazardAssessment? editing, string defaultGroupLabel,
+        AiPlanningService? ai = null, AiSettingsService? aiSettings = null, Unit? unit = null, Lesson? lesson = null)
+    {
+        _ai = ai; _aiSettings = aiSettings; _unit = unit; _lesson = lesson;
+        Substances.CollectionChanged += (_, _) => OnPropertyChanged(nameof(HasSubstances));
+        GroupLabel = defaultGroupLabel;
+        _editing = editing is not null;
+        if (editing is null) return;
+
+        Title = editing.Title;
+        GroupLabel = editing.GroupLabel;
+        DateText = editing.Date?.ToString("dd.MM.yyyy") ?? "";
+        KindName = ExperimentKindDisplay.Label(editing.Kind);
+        Procedure = editing.Procedure;
+        foreach (var s in editing.Substances) Substances.Add(NewSubstanceItem(s));
+        foreach (var h in editing.Hazards) Hazards.Add(h);
+        foreach (var m in editing.ProtectiveMeasures) ProtectiveMeasures.Add(m);
+        FirstAid = editing.FirstAid;
+        Disposal = editing.Disposal;
+        Notes = editing.Notes;
+        IsAiAssisted = editing.IsAiAssisted;
+    }
+
+    partial void OnIsAiBusyChanged(bool value) => OnPropertyChanged(nameof(AiButtonLabel));
+
+    partial void OnStepIndexChanged(int value)
+    {
+        OnPropertyChanged(nameof(StepTitle));
+        OnPropertyChanged(nameof(StepProgressLabel));
+        OnPropertyChanged(nameof(IsFirstStep));
+        OnPropertyChanged(nameof(IsLastStep));
+        OnPropertyChanged(nameof(IsBasicsStep));
+        OnPropertyChanged(nameof(IsSubstancesStep));
+        OnPropertyChanged(nameof(IsHazardsStep));
+        OnPropertyChanged(nameof(IsFirstAidStep));
+        OnPropertyChanged(nameof(IsSummaryStep));
+    }
+
+    private HazardSubstanceEditItem NewSubstanceItem(HazardSubstance? source = null)
+    {
+        var item = new HazardSubstanceEditItem(source) { OnRemove = RemoveSubstance };
+        return item;
+    }
+
+    [RelayCommand]
+    private void AddSubstance() => Substances.Add(NewSubstanceItem());
+
+    private void RemoveSubstance(HazardSubstanceEditItem item) => Substances.Remove(item);
+
+    [RelayCommand]
+    private void AddHazard()
+    {
+        if (string.IsNullOrWhiteSpace(NewHazard)) return;
+        Hazards.Add(NewHazard.Trim());
+        NewHazard = "";
+    }
+
+    [RelayCommand]
+    private void RemoveHazard(string? hazard) { if (hazard is not null) Hazards.Remove(hazard); }
+
+    [RelayCommand]
+    private void AddProtectiveMeasure()
+    {
+        if (string.IsNullOrWhiteSpace(NewProtectiveMeasure)) return;
+        ProtectiveMeasures.Add(NewProtectiveMeasure.Trim());
+        NewProtectiveMeasure = "";
+    }
+
+    [RelayCommand]
+    private void RemoveProtectiveMeasure(string? measure) { if (measure is not null) ProtectiveMeasures.Remove(measure); }
+
+    [RelayCommand]
+    private void Next()
+    {
+        if (IsFirstStep && string.IsNullOrWhiteSpace(Title))
+        {
+            TitleError = "Titel erforderlich.";
+            return;
+        }
+        TitleError = "";
+        if (!IsLastStep) StepIndex++;
+    }
+
+    [RelayCommand]
+    private void Back() { if (!IsFirstStep) StepIndex--; }
+
+    /// <summary>
+    /// Fragt einen KI-Entwurf zu genau dieser Lesson ab (Thema + Verlaufsplan als Kontext) und
+    /// übernimmt ihn in die Wizard-Felder — überschreibt dabei bewusst den aktuellen Stand, damit
+    /// nach einem erneuten Klick klar ist, was tatsächlich von der KI kommt. Die Lehrkraft prüft
+    /// und passt danach in den einzelnen Schritten an; der Rechtssicherheits-Hinweis wird über
+    /// <see cref="IsAiAssisted"/> in den PDF-Export übernommen.
+    /// </summary>
+    [RelayCommand]
+    private async Task RequestAiDraft()
+    {
+        if (!CanUseAi) return;
+        var token = _aiSettings!.GetToken();
+        if (token is null)
+        {
+            AiError = "Nicht angemeldet. Bitte in den Einstellungen bei der KI-Unterstützung anmelden.";
+            return;
+        }
+
+        AiError = ""; IsAiBusy = true;
+        try
+        {
+            var aiLesson = new AiLesson
+            {
+                Id = _lesson!.Id,
+                Date = _lesson.Date,
+                LessonNumber = _lesson.LessonNumber,
+                Topic = _lesson.Topic,
+                StartTime = _lesson.StartTime,
+                Phases = _lesson.Phases.Select(p => new AiPhaseStep
+                {
+                    Name = p.Name, DurationMinutes = p.DurationMinutes,
+                    Activity = p.Activity, Material = p.Material, Shorthand = p.Shorthand,
+                }).ToList(),
+            };
+
+            var response = await _ai!.RequestHazardAssessmentDraftAsync(_unit!, aiLesson, token);
+            ApplyAiResponse(response);
+        }
+        catch (AiBackendException ex)
+        {
+            AiError = ex.Message;
+        }
+        finally
+        {
+            IsAiBusy = false;
+        }
+    }
+
+    private void ApplyAiResponse(AiHazardAssessmentResponse response)
+    {
+        if (string.IsNullOrWhiteSpace(Title)) Title = _lesson?.Topic ?? "";
+        KindName = ExperimentKindDisplay.Label(ExperimentKindDisplay.FromWireValue(response.ExperimentKind));
+        Procedure = response.Procedure;
+
+        Substances.Clear();
+        foreach (var s in response.Substances)
+            Substances.Add(NewSubstanceItem(new HazardSubstance
+            {
+                Name = s.Name,
+                Amount = s.Amount,
+                HStatements = s.HStatements,
+                PStatements = s.PStatements,
+                GhsPictograms = s.GhsPictograms
+                    .Select(GhsPictogramDisplay.FromCode)
+                    .Where(p => p.HasValue)
+                    .Select(p => p!.Value)
+                    .ToList(),
+            }));
+
+        Hazards.Clear();
+        foreach (var h in response.Hazards) Hazards.Add(h);
+        ProtectiveMeasures.Clear();
+        foreach (var m in response.ProtectiveMeasures) ProtectiveMeasures.Add(m);
+        FirstAid = response.FirstAid;
+        Disposal = response.Disposal;
+        IsAiAssisted = true;
+    }
+
+    [RelayCommand]
+    private void Save()
+    {
+        if (string.IsNullOrWhiteSpace(Title))
+        {
+            TitleError = "Titel erforderlich.";
+            StepIndex = 0;
+            return;
+        }
+        TitleError = "";
+
+        DateOnly? date = null;
+        if (!string.IsNullOrWhiteSpace(DateText) &&
+            DateOnly.TryParseExact(DateText, "dd.MM.yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out var parsed))
+            date = parsed;
+
+        Result = new HazardAssessment
+        {
+            Title = Title.Trim(),
+            GroupLabel = GroupLabel.Trim(),
+            Date = date,
+            Kind = ExperimentKindDisplay.FromLabel(KindName),
+            Procedure = Procedure.Trim(),
+            Substances = Substances.Select(s => s.ToModel()).ToList(),
+            Hazards = Hazards.ToList(),
+            ProtectiveMeasures = ProtectiveMeasures.ToList(),
+            FirstAid = FirstAid.Trim(),
+            Disposal = Disposal.Trim(),
+            Notes = Notes.Trim(),
+            IsAiAssisted = IsAiAssisted,
+        };
+    }
+}

LehrerApp.Desktop/ViewModels/Groups/PlanningViewModels.cs

@@ -5,6 +5,7 @@ using LehrerApp.Core.Interfaces;
 using LehrerApp.Core.Models;
 using LehrerApp.Core.Services;
 using LehrerApp.Desktop.Services;
+using LehrerApp.Desktop.ViewModels.Students;
 using System.Collections.ObjectModel;
 using System.Globalization;
 
@@ -655,9 +656,11 @@ public partial class LessonDialogViewModel : ObservableObject
     private readonly IAlternativeLessonPathRepository _alternativePaths;
     private readonly ITimetableSlotRepository _timetableSlots;
     private readonly PeriodScheduleService _periodSchedule;
+    private readonly IAttachmentStorage _attachmentStorage;
     private readonly Guid _unitId;
     private readonly Guid _groupId;
     private readonly Lesson? _editingLesson;
+    private readonly List<string> _newlyUploadedStorageIds = [];
 
     [ObservableProperty] private string _dateText = DateOnly.FromDateTime(DateTime.Today).ToString("dd.MM.yyyy");
     [ObservableProperty] private int? _lessonNumber;
@@ -684,6 +687,10 @@ public partial class LessonDialogViewModel : ObservableObject
     public string[] ShorthandSuggestions { get; }
     public ObservableCollection<PhaseStepEditItem> Phases { get; } = [];
 
+    // Anhänge (Material/Arbeitsblätter, Experiment-/Gefährdungsbeurteilungsdokumente).
+    public ObservableCollection<AttachmentItem> Attachments { get; } = [];
+    [ObservableProperty] private string _attachmentError = "";
+
     /// Vom Code-Behind gesetzt (Fenster als Owner für den Zuweisen-Dialog): fragt nach dem
     /// alternativen Ablauf, dem eine Phase zugeordnet werden soll (Auswahl oder Neuanlage
     /// per Combobox-Dialog). null zurückgegeben = abgebrochen.
@@ -713,11 +720,13 @@ public partial class LessonDialogViewModel : ObservableObject
 
     public LessonDialogViewModel(ILessonRepository lessons, IShorthandCodeRepository shorthandCodes,
         IAlternativeLessonPathRepository alternativePaths, ITimetableSlotRepository timetableSlots,
-        PeriodScheduleService periodSchedule, Guid unitId, Guid groupId, string groupName, string subjectName,
+        PeriodScheduleService periodSchedule, IAttachmentStorage attachmentStorage,
+        Guid unitId, Guid groupId, string groupName, string subjectName,
         List<string> materialSuggestions, List<string> shorthandHistorySuggestions, Lesson? editingLesson)
     {
         _lessons = lessons; _alternativePaths = alternativePaths;
         _timetableSlots = timetableSlots; _periodSchedule = periodSchedule;
+        _attachmentStorage = attachmentStorage;
         _unitId = unitId; _groupId = groupId; _editingLesson = editingLesson;
         GroupSubjectDisplay = string.IsNullOrWhiteSpace(subjectName)
             ? $"{groupName} · kein Fach hinterlegt (siehe Lerngruppe)" : $"{groupName} · {subjectName}";
@@ -746,6 +755,8 @@ public partial class LessonDialogViewModel : ObservableObject
             Reflection    = editingLesson.Reflection ?? "";
             StatusName    = LessonStatusDisplay.ToName(editingLesson.Status);
             foreach (var p in editingLesson.Phases) AddPhaseInternal(p);
+            foreach (var att in editingLesson.Attachments)
+                Attachments.Add(new AttachmentItem(att.StorageId, att.FileName, att.SizeBytes, att.UploadedAt));
         }
         else
         {
@@ -925,6 +936,39 @@ public partial class LessonDialogViewModel : ObservableObject
         _      => "#B71C1C", // Dunkelrot: deutlich überplant
     };
 
+    // ── Anhänge ────────────────────────────────────────────────────────────
+
+    public void AddAttachment(string fileName, Stream content)
+    {
+        AttachmentError = "";
+        if (content.Length > IAttachmentStorage.MaxSizeBytes)
+        {
+            AttachmentError = $"Datei zu groß (max. {IAttachmentStorage.MaxSizeBytes / 1024 / 1024} MB).";
+            return;
+        }
+        var storageId = _attachmentStorage.Upload(fileName, content);
+        _newlyUploadedStorageIds.Add(storageId);
+        Attachments.Add(new AttachmentItem(storageId, fileName, content.Length, DateTime.UtcNow));
+    }
+
+    public Stream? OpenAttachment(AttachmentItem item) => _attachmentStorage.OpenRead(item.StorageId);
+
+    [RelayCommand]
+    private void RemoveAttachment(AttachmentItem? item)
+    {
+        if (item is null) return;
+        _attachmentStorage.Delete(item.StorageId);
+        _newlyUploadedStorageIds.Remove(item.StorageId);
+        Attachments.Remove(item);
+    }
+
+    /// Vom Code-Behind beim Abbrechen aufgerufen: neu hochgeladene, nie gespeicherte Anhänge
+    /// wieder entfernen, damit keine verwaisten Blobs in der Datenbank zurückbleiben.
+    public void DiscardUnsavedAttachments()
+    {
+        foreach (var id in _newlyUploadedStorageIds) _attachmentStorage.Delete(id);
+    }
+
     [RelayCommand]
     private void Save()
     {
@@ -960,7 +1004,12 @@ public partial class LessonDialogViewModel : ObservableObject
         Result.HomeworkCheckDismissed = HomeworkCheckDismissed;
         Result.Reflection   = string.IsNullOrWhiteSpace(Reflection) ? null : Reflection.Trim();
         Result.Status       = LessonStatusDisplay.FromName(StatusName);
+        Result.Attachments  = Attachments.Select(a => new DocumentAttachment
+        {
+            StorageId = a.StorageId, FileName = a.FileName, SizeBytes = a.SizeBytes, UploadedAt = a.UploadedAt,
+        }).ToList();
         _lessons.Save(Result);
+        _newlyUploadedStorageIds.Clear();
     }
 }
 

LehrerApp.Desktop/ViewModels/Groups/SeatingPlanViewModels.cs

@@ -398,6 +398,40 @@ public partial class SeatingPlanTabViewModel : ObservableObject
         ReloadPlans();
     }
 
+    /// <summary>
+    /// Klausur-Sitzplan mischen (14, Nutzer-Idee): erzeugt aus dem aktuell gewählten Plan einen
+    /// neuen, unabhängigen Plan mit gleichem Raster/Raum, aber zufällig vertauschten Insassen der
+    /// belegten Plätze (Fisher-Yates via <see cref="Random.Shared"/>) — die Platzkoordinaten selbst
+    /// bleiben unverändert, nur wer wo sitzt wird neu gewürfelt. Der ursprüngliche Plan bleibt
+    /// unangetastet erhalten, damit er bei Bedarf für den nächsten regulären Unterricht weiter
+    /// genutzt werden kann.
+    /// </summary>
+    [RelayCommand(CanExecute = nameof(CanEditSelected))]
+    private void ShuffleSeats()
+    {
+        if (_currentPlan is null) return;
+
+        var studentIds = _currentPlan.Assignments.Select(a => a.StudentId).ToArray();
+        Random.Shared.Shuffle(studentIds);
+
+        var shuffled = new SeatingPlan
+        {
+            GroupId = _currentPlan.GroupId,
+            Name = $"{_currentPlan.Name} (Klausur gemischt {DateTime.Now:dd.MM. HH:mm})",
+            Room = _currentPlan.Room,
+            Rows = _currentPlan.Rows,
+            Columns = _currentPlan.Columns,
+            ColumnGapWidths = [.. _currentPlan.ColumnGapWidths],
+            IsBoardAtBottom = _currentPlan.IsBoardAtBottom,
+            HiddenSeats = _currentPlan.HiddenSeats.Select(h => new HiddenSeat { Row = h.Row, Column = h.Column }).ToList(),
+            Assignments = _currentPlan.Assignments
+                .Select((a, i) => new SeatAssignment { Row = a.Row, Column = a.Column, StudentId = studentIds[i] })
+                .ToList(),
+        };
+        _plans.Save(shuffled);
+        ReloadPlans(shuffled.Id);
+    }
+
     partial void OnIsEditModeChanged(bool value)
     {
         OnPropertyChanged(nameof(CanEditLayout));
@@ -417,6 +451,7 @@ public partial class SeatingPlanTabViewModel : ObservableObject
         AddPlanCommand.NotifyCanExecuteChanged();
         EditPlanCommand.NotifyCanExecuteChanged();
         DeletePlanCommand.NotifyCanExecuteChanged();
+        ShuffleSeatsCommand.NotifyCanExecuteChanged();
     }
 }
 

LehrerApp.Desktop/ViewModels/Students/DocumentationViewModels.cs

@@ -401,11 +401,17 @@ public partial class DocumentationDialogViewModel : ObservableObject
 
 public class AttachmentItem(string storageId, string fileName, long sizeBytes, DateTime uploadedAt)
 {
+    public const string HazardAssessmentSuffix = ".gbu.json";
+
     public string StorageId { get; } = storageId;
     public string FileName { get; } = fileName;
     public long SizeBytes { get; } = sizeBytes;
     public DateTime UploadedAt { get; } = uploadedAt;
     public string SizeDisplay => $"{SizeBytes / 1024.0:0} KB";
+    /// Strukturierter Gefährdungsbeurteilungs-Anhang (siehe HazardAssessment) statt einer
+    /// beliebigen hochgeladenen Datei — steuert im Anhang-Editor, ob "Öffnen"+"PDF" statt des
+    /// generischen "Speichern" angeboten wird.
+    public bool IsHazardAssessment => FileName.EndsWith(HazardAssessmentSuffix, StringComparison.OrdinalIgnoreCase);
 }
 
 public class TagChip(string text)

LehrerApp.Desktop/Views/Groups/HazardAssessmentWizardDialog.axaml

@@ -0,0 +1,203 @@
+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:vm="clr-namespace:LehrerApp.Desktop.ViewModels.Groups"
+        x:Class="LehrerApp.Desktop.Views.Groups.HazardAssessmentWizardDialog"
+        x:DataType="vm:HazardAssessmentWizardViewModel"
+        Title="{Binding DialogTitle}"
+        Width="720" Height="720" MinWidth="600" MinHeight="480"
+        CanResize="True" WindowStartupLocation="CenterOwner">
+
+  <Grid RowDefinitions="Auto,Auto,*,Auto" Margin="24">
+    <StackPanel Grid.Row="0" Spacing="2" Margin="0,0,0,10">
+      <TextBlock Text="{Binding DialogTitle}" Classes="dialogtitle"/>
+      <TextBlock FontSize="12" Opacity="0.7">
+        <Run Text="{Binding StepProgressLabel}"/>
+        <Run Text=" · "/>
+        <Run Text="{Binding StepTitle}" FontWeight="SemiBold"/>
+      </TextBlock>
+    </StackPanel>
+
+    <Border Grid.Row="1" IsVisible="{Binding CanUseAi}" Background="#FFF3E0" CornerRadius="6"
+            Padding="10" Margin="0,0,0,10">
+      <Grid ColumnDefinitions="*,Auto">
+        <StackPanel Grid.Column="0" Spacing="2">
+          <TextBlock FontSize="12" TextWrapping="Wrap">
+            <Run Text="🤖 KI-Entwurf auf Basis von Thema und Verlaufsplan dieser Stunde." FontWeight="SemiBold"/>
+            <LineBreak/>
+            <Run Text="⚠️ Kein rechtssicheres Dokument — bitte jede Angabe (insbesondere H-/P-Sätze und Mengen) eigenverantwortlich gegen das Sicherheitsdatenblatt prüfen, bevor du die Gefährdungsbeurteilung verwendest."/>
+          </TextBlock>
+          <TextBlock Text="{Binding AiError}" Foreground="Red" FontSize="11"
+                     IsVisible="{Binding AiError, Converter={x:Static StringConverters.IsNotNullOrEmpty}}"/>
+        </StackPanel>
+        <Button Grid.Column="1" Content="{Binding AiButtonLabel}" Command="{Binding RequestAiDraftCommand}"
+                IsEnabled="{Binding !IsAiBusy}" VerticalAlignment="Top" Margin="10,0,0,0"/>
+      </Grid>
+    </Border>
+
+    <ScrollViewer Grid.Row="2">
+      <StackPanel Spacing="14" Margin="0,0,12,0">
+
+        <!-- Schritt 1: Basisdaten -->
+        <StackPanel Spacing="10" IsVisible="{Binding IsBasicsStep}">
+          <StackPanel Spacing="4">
+            <TextBlock Text="Titel *" FontSize="12" Opacity="0.7"/>
+            <TextBox Text="{Binding Title}" PlaceholderText="z.B. Natrium in Wasser"/>
+            <TextBlock Text="{Binding TitleError}" Foreground="Red" FontSize="11"
+                       IsVisible="{Binding TitleError, Converter={x:Static StringConverters.IsNotNullOrEmpty}}"/>
+          </StackPanel>
+          <Grid ColumnDefinitions="*,12,*,12,*">
+            <StackPanel Grid.Column="0" Spacing="4">
+              <TextBlock Text="Klassenstufe/Kurs" FontSize="12" Opacity="0.7"/>
+              <TextBox Text="{Binding GroupLabel}"/>
+            </StackPanel>
+            <StackPanel Grid.Column="2" Spacing="4">
+              <TextBlock Text="Datum" FontSize="12" Opacity="0.7"/>
+              <TextBox Text="{Binding DateText}" PlaceholderText="TT.MM.JJJJ"/>
+            </StackPanel>
+            <StackPanel Grid.Column="4" Spacing="4">
+              <TextBlock Text="Art des Versuchs" FontSize="12" Opacity="0.7"/>
+              <ComboBox ItemsSource="{Binding KindOptions}" SelectedItem="{Binding KindName}"
+                        HorizontalAlignment="Stretch"/>
+            </StackPanel>
+          </Grid>
+          <StackPanel Spacing="4">
+            <TextBlock Text="Durchführung (Kurzbeschreibung)" FontSize="12" Opacity="0.7"/>
+            <TextBox Text="{Binding Procedure}" AcceptsReturn="True" TextWrapping="Wrap" Height="90"/>
+          </StackPanel>
+        </StackPanel>
+
+        <!-- Schritt 2: Gefahrstoffe -->
+        <StackPanel Spacing="10" IsVisible="{Binding IsSubstancesStep}">
+          <Grid ColumnDefinitions="*,Auto">
+            <TextBlock Grid.Column="0" Text="Verwendete Gefahrstoffe" FontSize="13" FontWeight="SemiBold"
+                       VerticalAlignment="Center"/>
+            <Button Grid.Column="1" Content="＋ Stoff" Command="{Binding AddSubstanceCommand}"/>
+          </Grid>
+          <TextBlock Text="Noch keine Gefahrstoffe erfasst." Classes="emptyhint"
+                     IsVisible="{Binding !HasSubstances}"/>
+          <ItemsControl ItemsSource="{Binding Substances}">
+            <ItemsControl.ItemTemplate>
+              <DataTemplate x:DataType="vm:HazardSubstanceEditItem">
+                <Border BorderBrush="{DynamicResource SystemControlForegroundBaseLowBrush}"
+                        BorderThickness="0,0,0,1" Padding="0,10">
+                  <StackPanel Spacing="6">
+                    <Grid ColumnDefinitions="*,140,Auto">
+                      <TextBox Grid.Column="0" Text="{Binding Name}" PlaceholderText="Stoffname"
+                                Margin="0,0,8,0"/>
+                      <TextBox Grid.Column="1" Text="{Binding Amount}" PlaceholderText="Menge, z.B. ca. 2 g"
+                                Margin="0,0,8,0"/>
+                      <Button Grid.Column="2" Content="✕" Command="{Binding RemoveCommand}"
+                              ToolTip.Tip="Stoff entfernen"/>
+                    </Grid>
+                    <ItemsControl ItemsSource="{Binding PictogramOptions}">
+                      <ItemsControl.ItemsPanel>
+                        <ItemsPanelTemplate><WrapPanel ItemSpacing="10" LineSpacing="4"/></ItemsPanelTemplate>
+                      </ItemsControl.ItemsPanel>
+                      <ItemsControl.ItemTemplate>
+                        <DataTemplate x:DataType="vm:GhsPictogramOption">
+                          <CheckBox Content="{Binding Label}" IsChecked="{Binding IsSelected}" FontSize="12"/>
+                        </DataTemplate>
+                      </ItemsControl.ItemTemplate>
+                    </ItemsControl>
+                    <Grid ColumnDefinitions="*,12,*">
+                      <StackPanel Grid.Column="0" Spacing="2">
+                        <TextBlock Text="H-Sätze" FontSize="11" Opacity="0.6"/>
+                        <TextBox Text="{Binding HStatements}" PlaceholderText="z.B. H314, H290"/>
+                      </StackPanel>
+                      <StackPanel Grid.Column="2" Spacing="2">
+                        <TextBlock Text="P-Sätze" FontSize="11" Opacity="0.6"/>
+                        <TextBox Text="{Binding PStatements}" PlaceholderText="z.B. P280, P305+P351+P338"/>
+                      </StackPanel>
+                    </Grid>
+                  </StackPanel>
+                </Border>
+              </DataTemplate>
+            </ItemsControl.ItemTemplate>
+          </ItemsControl>
+        </StackPanel>
+
+        <!-- Schritt 3: Gefährdungen & Schutzmaßnahmen -->
+        <StackPanel Spacing="14" IsVisible="{Binding IsHazardsStep}">
+          <StackPanel Spacing="6">
+            <TextBlock Text="Identifizierte Gefährdungen" FontSize="13" FontWeight="SemiBold"/>
+            <ItemsControl ItemsSource="{Binding Hazards}">
+              <ItemsControl.ItemTemplate>
+                <DataTemplate x:DataType="x:String">
+                  <Grid ColumnDefinitions="*,Auto" Margin="0,2">
+                    <TextBlock Grid.Column="0" Text="{Binding}" VerticalAlignment="Center"/>
+                    <Button Grid.Column="1" Content="×" FontSize="13" Padding="7,2"
+                            Command="{Binding $parent[ItemsControl].((vm:HazardAssessmentWizardViewModel)DataContext).RemoveHazardCommand}"
+                            CommandParameter="{Binding}"/>
+                  </Grid>
+                </DataTemplate>
+              </ItemsControl.ItemTemplate>
+            </ItemsControl>
+            <Grid ColumnDefinitions="*,8,Auto">
+              <TextBox Grid.Column="0" Text="{Binding NewHazard}" PlaceholderText="z.B. Verätzungsgefahr an Haut/Augen"/>
+              <Button Grid.Column="2" Content="＋" Command="{Binding AddHazardCommand}"/>
+            </Grid>
+          </StackPanel>
+          <StackPanel Spacing="6">
+            <TextBlock Text="Schutzmaßnahmen" FontSize="13" FontWeight="SemiBold"/>
+            <ItemsControl ItemsSource="{Binding ProtectiveMeasures}">
+              <ItemsControl.ItemTemplate>
+                <DataTemplate x:DataType="x:String">
+                  <Grid ColumnDefinitions="*,Auto" Margin="0,2">
+                    <TextBlock Grid.Column="0" Text="{Binding}" VerticalAlignment="Center"/>
+                    <Button Grid.Column="1" Content="×" FontSize="13" Padding="7,2"
+                            Command="{Binding $parent[ItemsControl].((vm:HazardAssessmentWizardViewModel)DataContext).RemoveProtectiveMeasureCommand}"
+                            CommandParameter="{Binding}"/>
+                  </Grid>
+                </DataTemplate>
+              </ItemsControl.ItemTemplate>
+            </ItemsControl>
+            <Grid ColumnDefinitions="*,8,Auto">
+              <TextBox Grid.Column="0" Text="{Binding NewProtectiveMeasure}" PlaceholderText="z.B. Schutzbrille, Handschuhe, Abzug"/>
+              <Button Grid.Column="2" Content="＋" Command="{Binding AddProtectiveMeasureCommand}"/>
+            </Grid>
+          </StackPanel>
+        </StackPanel>
+
+        <!-- Schritt 4: Erste Hilfe & Entsorgung -->
+        <StackPanel Spacing="10" IsVisible="{Binding IsFirstAidStep}">
+          <StackPanel Spacing="4">
+            <TextBlock Text="Erste Hilfe" FontSize="12" Opacity="0.7"/>
+            <TextBox Text="{Binding FirstAid}" AcceptsReturn="True" TextWrapping="Wrap" Height="90"/>
+          </StackPanel>
+          <StackPanel Spacing="4">
+            <TextBlock Text="Entsorgung" FontSize="12" Opacity="0.7"/>
+            <TextBox Text="{Binding Disposal}" AcceptsReturn="True" TextWrapping="Wrap" Height="70"/>
+          </StackPanel>
+          <StackPanel Spacing="4">
+            <TextBlock Text="Weitere Hinweise" FontSize="12" Opacity="0.7"/>
+            <TextBox Text="{Binding Notes}" AcceptsReturn="True" TextWrapping="Wrap" Height="60"/>
+          </StackPanel>
+        </StackPanel>
+
+        <!-- Schritt 5: Zusammenfassung -->
+        <StackPanel Spacing="8" IsVisible="{Binding IsSummaryStep}">
+          <TextBlock Text="{Binding Title}" FontSize="15" FontWeight="SemiBold"/>
+          <TextBlock FontSize="12" Opacity="0.7">
+            <Run Text="{Binding GroupLabel}"/>
+            <Run Text=" · "/>
+            <Run Text="{Binding KindName}"/>
+          </TextBlock>
+          <TextBlock Text="{Binding Procedure}" TextWrapping="Wrap"/>
+          <TextBlock Text="{Binding Substances.Count, StringFormat='{}{0} Gefahrstoff(e) erfasst'}" FontSize="12"/>
+          <TextBlock Text="Alle Angaben vor dem Einsatz noch einmal gegenprüfen." FontSize="12" Opacity="0.7"
+                     IsVisible="{Binding IsAiAssisted}"/>
+        </StackPanel>
+
+      </StackPanel>
+    </ScrollViewer>
+
+    <Grid Grid.Row="3" ColumnDefinitions="Auto,*,Auto,8,Auto,8,Auto" Margin="0,16,0,0">
+      <Button Grid.Column="0" Content="Abbrechen" Click="OnCancel"/>
+      <Button Grid.Column="2" Content="Zurück" Command="{Binding BackCommand}"
+              IsVisible="{Binding !IsFirstStep}"/>
+      <Button Grid.Column="4" Content="Weiter" Command="{Binding NextCommand}"
+              IsVisible="{Binding !IsLastStep}"/>
+      <Button Grid.Column="6" Content="Speichern" Click="OnSave" IsVisible="{Binding IsLastStep}"/>
+    </Grid>
+  </Grid>
+</Window>

LehrerApp.Desktop/Views/Groups/HazardAssessmentWizardDialog.axaml.cs

@@ -0,0 +1,21 @@
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+using LehrerApp.Desktop.ViewModels.Groups;
+
+namespace LehrerApp.Desktop.Views.Groups;
+
+public partial class HazardAssessmentWizardDialog : Window
+{
+    public HazardAssessmentWizardDialog() => InitializeComponent();
+
+    private void OnSave(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is HazardAssessmentWizardViewModel vm)
+        {
+            vm.SaveCommand.Execute(null);
+            if (vm.Result is not null) Close(true);
+        }
+    }
+
+    private void OnCancel(object? sender, RoutedEventArgs e) => Close(false);
+}

LehrerApp.Desktop/Views/Groups/LessonDialog.axaml

@@ -1,6 +1,7 @@
 <Window xmlns="https://github.com/avaloniaui"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:vm="clr-namespace:LehrerApp.Desktop.ViewModels.Groups"
+        xmlns:vms="clr-namespace:LehrerApp.Desktop.ViewModels.Students"
         x:Class="LehrerApp.Desktop.Views.Groups.LessonDialog"
         x:DataType="vm:LessonDialogViewModel"
         Title="{Binding DialogTitle}"
@@ -139,6 +140,43 @@
           <TextBox Text="{Binding Reflection}" AcceptsReturn="True" Height="56" TextWrapping="Wrap"
                     PlaceholderText="Nach der Stunde: was lief gut, was nicht?"/>
         </StackPanel>
+
+        <Separator Margin="0,4"/>
+
+        <StackPanel Spacing="6">
+          <Grid ColumnDefinitions="*,Auto">
+            <TextBlock Grid.Column="0" Text="Anhänge (Material, Arbeitsblätter, Experiment-/Gefährdungsbeurteilung)"
+                       FontSize="12" Opacity="0.7" VerticalAlignment="Center"/>
+            <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="6">
+              <Button Content="🧪 Gefährdungsbeurteilung" FontSize="12" Padding="8,4" Click="OnCreateHazardAssessment"/>
+              <Button Content="＋ Datei" FontSize="12" Padding="8,4" Click="OnAddAttachment"/>
+            </StackPanel>
+          </Grid>
+          <ItemsControl ItemsSource="{Binding Attachments}">
+            <ItemsControl.ItemTemplate>
+              <DataTemplate x:DataType="vms:AttachmentItem">
+                <Grid ColumnDefinitions="*,Auto,Auto,Auto,Auto" Margin="0,2">
+                  <TextBlock Grid.Column="0" Text="{Binding FileName}" VerticalAlignment="Center" FontSize="13"
+                             TextTrimming="CharacterEllipsis"/>
+                  <TextBlock Grid.Column="1" Text="{Binding SizeDisplay}" VerticalAlignment="Center"
+                             FontSize="11" Opacity="0.5" Margin="6,0"/>
+                  <Button Grid.Column="2" Content="Öffnen" FontSize="11" Padding="7,2" Margin="0,0,4,0"
+                          Click="OnOpenHazardAssessment" Tag="{Binding}" IsVisible="{Binding IsHazardAssessment}"/>
+                  <Button Grid.Column="2" Content="Speichern" FontSize="11" Padding="7,2" Margin="0,0,4,0"
+                          Click="OnOpenAttachment" Tag="{Binding}" IsVisible="{Binding !IsHazardAssessment}"/>
+                  <Button Grid.Column="3" Content="PDF" FontSize="11" Padding="7,2" Margin="0,0,4,0"
+                          Click="OnPrintHazardAssessment" Tag="{Binding}"
+                          IsVisible="{Binding IsHazardAssessment}"/>
+                  <Button Grid.Column="4" Content="×" FontSize="13" Padding="7,2"
+                          Command="{Binding $parent[ItemsControl].((vm:LessonDialogViewModel)DataContext).RemoveAttachmentCommand}"
+                          CommandParameter="{Binding}"/>
+                </Grid>
+              </DataTemplate>
+            </ItemsControl.ItemTemplate>
+          </ItemsControl>
+          <TextBlock Text="{Binding AttachmentError}" Foreground="Red" FontSize="11"
+                     IsVisible="{Binding AttachmentError, Converter={x:Static StringConverters.IsNotNullOrEmpty}}"/>
+        </StackPanel>
       </StackPanel>
     </ScrollViewer>
 

LehrerApp.Desktop/Views/Groups/LessonDialog.axaml.cs

@@ -1,9 +1,11 @@
 using Avalonia.Controls;
 using Avalonia.Interactivity;
+using Avalonia.Platform.Storage;
 using LehrerApp.Core.Interfaces;
 using LehrerApp.Core.Models;
 using LehrerApp.Desktop.Services;
 using LehrerApp.Desktop.ViewModels.Groups;
+using LehrerApp.Desktop.ViewModels.Students;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace LehrerApp.Desktop.Views.Groups;
@@ -38,7 +40,136 @@ public partial class LessonDialog : Window
         }
     }
 
-    private void OnCancel(object? s, RoutedEventArgs e) => Close(false);
+    private void OnCancel(object? s, RoutedEventArgs e)
+    {
+        if (DataContext is LessonDialogViewModel vm) vm.DiscardUnsavedAttachments();
+        Close(false);
+    }
+
+    private async void OnAddAttachment(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not LessonDialogViewModel vm) return;
+
+        var files = await StorageProvider.OpenFilePickerAsync(new FilePickerOpenOptions
+        {
+            Title = "Anhang auswählen", AllowMultiple = false,
+        });
+        if (files.Count == 0) return;
+
+        await using var stream = await files[0].OpenReadAsync();
+        vm.AddAttachment(files[0].Name, stream);
+    }
+
+    private async void OnOpenAttachment(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not LessonDialogViewModel vm) return;
+        if (sender is not Button { Tag: AttachmentItem item }) return;
+
+        using var source = vm.OpenAttachment(item);
+        if (source is null) return;
+
+        var file = await StorageProvider.SaveFilePickerAsync(new FilePickerSaveOptions
+        {
+            Title = "Anhang speichern unter", SuggestedFileName = item.FileName,
+        });
+        if (file is null) return;
+
+        await using var target = await file.OpenWriteAsync();
+        await source.CopyToAsync(target);
+    }
+
+    private async void OnCreateHazardAssessment(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not LessonDialogViewModel vm) return;
+
+        var (unit, contextLesson, groupName) = BuildHazardAssessmentContext(vm);
+        var dialogVm = new HazardAssessmentWizardViewModel(null, groupName,
+            App.Services.GetRequiredService<AiPlanningService>(), App.Services.GetRequiredService<AiSettingsService>(),
+            unit, contextLesson);
+        var dialog = new HazardAssessmentWizardDialog { DataContext = dialogVm };
+        var ok = await dialog.ShowDialog<bool>(this);
+        if (!ok || dialogVm.Result is null) return;
+
+        UploadHazardAssessment(vm, dialogVm.Result);
+    }
+
+    private async void OnOpenHazardAssessment(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not LessonDialogViewModel vm) return;
+        if (sender is not Button { Tag: AttachmentItem item }) return;
+
+        var editing = await ReadHazardAssessmentAsync(vm, item);
+        if (editing is null) return;
+
+        var (unit, contextLesson, _) = BuildHazardAssessmentContext(vm);
+        var dialogVm = new HazardAssessmentWizardViewModel(editing, editing.GroupLabel,
+            App.Services.GetRequiredService<AiPlanningService>(), App.Services.GetRequiredService<AiSettingsService>(),
+            unit, contextLesson);
+        var dialog = new HazardAssessmentWizardDialog { DataContext = dialogVm };
+        var ok = await dialog.ShowDialog<bool>(this);
+        if (!ok || dialogVm.Result is null) return;
+
+        vm.RemoveAttachmentCommand.Execute(item);
+        UploadHazardAssessment(vm, dialogVm.Result);
+    }
+
+    private async void OnPrintHazardAssessment(object? sender, RoutedEventArgs e)
+    {
+        var topLevel = TopLevel.GetTopLevel(this);
+        if (topLevel is null || DataContext is not LessonDialogViewModel vm) return;
+        if (sender is not Button { Tag: AttachmentItem item }) return;
+
+        var assessment = await ReadHazardAssessmentAsync(vm, item);
+        if (assessment is null) return;
+
+        var data = new HazardAssessmentPrintData(
+            assessment.Title, assessment.GroupLabel, assessment.Date?.ToString("dd.MM.yyyy") ?? "",
+            ExperimentKindDisplay.Label(assessment.Kind), assessment.Procedure,
+            assessment.Substances.Select(s => new HazardSubstancePrintRow(
+                s.Name, s.Amount, string.Join(", ", s.GhsPictograms.Select(GhsPictogramDisplay.Code)),
+                s.HStatements, s.PStatements)).ToList(),
+            assessment.Hazards, assessment.ProtectiveMeasures, assessment.FirstAid, assessment.Disposal,
+            assessment.Notes, assessment.IsAiAssisted);
+        var pdf = App.Services.GetRequiredService<PdfExportService>().BuildHazardAssessmentPdf(data);
+
+        await App.Services.GetRequiredService<ExportService>().SaveAsync(topLevel.StorageProvider,
+            ExportFile.Pdf("Gefährdungsbeurteilung als PDF speichern", $"GBU_{assessment.Title}", pdf));
+    }
+
+    /// Baut den Kontext für den Gefährdungsbeurteilungs-Assistenten (KI-Anfrage + Vorbelegung) aus
+    /// dem gerade im Dialog bearbeiteten, ggf. noch nicht gespeicherten Stand — funktioniert damit
+    /// auch beim Neuanlegen einer Stunde, bevor überhaupt gespeichert wurde.
+    private (Unit? Unit, Lesson ContextLesson, string GroupName) BuildHazardAssessmentContext(LessonDialogViewModel vm)
+    {
+        var unit = App.Services.GetRequiredService<IUnitRepository>().GetById(vm.UnitId);
+        var groupName = unit is null ? "" : App.Services.GetRequiredService<IGroupRepository>().GetById(unit.GroupId)?.Name ?? "";
+        var contextLesson = new Lesson { Topic = vm.Topic, Phases = vm.Phases.Select(p => p.ToModel()).ToList() };
+        return (unit, contextLesson, groupName);
+    }
+
+    private static async Task<HazardAssessment?> ReadHazardAssessmentAsync(LessonDialogViewModel vm, AttachmentItem item)
+    {
+        using var source = vm.OpenAttachment(item);
+        if (source is null) return null;
+        using var reader = new StreamReader(source);
+        var json = await reader.ReadToEndAsync();
+        return System.Text.Json.JsonSerializer.Deserialize<HazardAssessment>(json);
+    }
+
+    private static void UploadHazardAssessment(LessonDialogViewModel vm, HazardAssessment result)
+    {
+        var json = System.Text.Json.JsonSerializer.Serialize(result);
+        using var stream = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(json));
+        vm.AddAttachment(HazardAssessmentFileName(result.Title), stream);
+    }
+
+    private static string HazardAssessmentFileName(string title)
+    {
+        var invalid = Path.GetInvalidFileNameChars();
+        var safe = new string(title.Select(c => invalid.Contains(c) ? '_' : c).ToArray()).Trim();
+        if (safe.Length == 0) safe = "Gefaehrdungsbeurteilung";
+        return safe + AttachmentItem.HazardAssessmentSuffix;
+    }
 
     /// KI-Unterstützung mit Fokus auf genau diese (bereits gespeicherte) Stunde, statt den Umweg
     /// über die Einheiten-Übersicht nehmen zu müssen (4.5.22, Nutzer-Feedback). Die Übernahme im

LehrerApp.Desktop/Views/Groups/PlanningTabView.axaml.cs

@@ -99,6 +99,7 @@ public partial class PlanningTabView : UserControl
             App.Services.GetRequiredService<IAlternativeLessonPathRepository>(),
             App.Services.GetRequiredService<ITimetableSlotRepository>(),
             App.Services.GetRequiredService<PeriodScheduleService>(),
+            App.Services.GetRequiredService<IAttachmentStorage>(),
             unitId, groupId, vm.GroupLabel, vm.SubjectName,
             materialSuggestions, shorthandHistorySuggestions, editingLesson);
 

LehrerApp.Desktop/Views/Groups/SeatingPlanTabView.axaml

@@ -51,6 +51,9 @@
             <Button Grid.Column="2" Content="Löschen" Command="{Binding DeletePlanCommand}"
                     HorizontalAlignment="Stretch"/>
           </Grid>
+          <Button Content="🎲 Plätze für Klausur mischen" Command="{Binding ShuffleSeatsCommand}"
+                  HorizontalAlignment="Stretch" IsVisible="{Binding HasSelectedPlan}"
+                  ToolTip.Tip="Legt einen neuen, unabhängigen Sitzplan mit demselben Raster an, in dem die belegten Plätze zufällig neu vertauscht sind. Der ursprüngliche Plan bleibt unverändert erhalten."/>
         </StackPanel>
       </Grid>
     </Border>