feat: Formulare-Menü mit Elternbrief-Einstieg + Arbeitsblatt-Personalisierung (Nutzer-Feedback)

Neue Menü-Kategorie "Formulare" in der Menüleiste: "Elternbrief erzeugen..." öffnet
jetzt einen Schüler-Picker statt nur aus der Schülerdetailansicht erreichbar zu sein,
"Arbeitsblatt personalisieren..." ist aktiv, sobald eine einzelne Lerngruppe geöffnet
ist, und erzeugt aus einer in TemplateDesigner gebauten .lavorlage-Vorlage ein PDF je
aktivem Gruppenmitglied - über eine von den Elternbrief-Vorlagen getrennte
WorksheetTemplateStore-Bibliothek.

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

LehrerApp.Desktop/ViewModels/Groups/PersonalizeWorksheetDialogViewModel.cs

@@ -0,0 +1,86 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using LehrerApp.Core.Interfaces;
+using LehrerApp.Core.Models;
+using LehrerApp.Desktop.Services;
+using LehrerApp.Desktop.ViewModels.Students;
+using LehrerApp.Templating;
+using System.Collections.ObjectModel;
+
+namespace LehrerApp.Desktop.ViewModels.Groups;
+
+/// <summary>Erzeugt aus einer in TemplateDesigner gebauten Arbeitsblatt-.lavorlage-Vorlage ein
+/// personalisiertes PDF je aktivem Mitglied der aktuell geöffneten Lerngruppe. Nutzt bewusst
+/// dieselbe Platzhalter-/Rendering-Infrastruktur wie der Elternbrief-Dialog
+/// (<see cref="LetterPlaceholderBuilder"/>, <see cref="ITemplateRenderer"/>), aber eine getrennte
+/// <see cref="WorksheetTemplateStore"/>-Vorlagenbibliothek.</summary>
+public partial class PersonalizeWorksheetDialogViewModel : ObservableObject
+{
+    private readonly LearningGroup _group;
+    private readonly WorksheetTemplateStore _templates;
+    private readonly ITemplateRenderer _renderer;
+
+    [ObservableProperty] private LetterTemplateChoice? _selectedTemplate;
+    [ObservableProperty] private string _statusMessage = "";
+
+    public string GroupName => $"{_group.Name} · {_group.SchoolYear}";
+    public ObservableCollection<LetterTemplateChoice> Templates { get; } = [];
+    public ObservableCollection<WorksheetStudentChoice> Students { get; } = [];
+    public ObservableCollection<WorksheetGenerationResult> Results { get; } = [];
+    public bool HasNoTemplates => Templates.Count == 0;
+    public bool HasResults => Results.Count > 0;
+
+    public PersonalizeWorksheetDialogViewModel(LearningGroup group, IReadOnlyList<Guid> studentIds,
+        IStudentRepository students, WorksheetTemplateStore templates, ITemplateRenderer renderer)
+    {
+        _group = group; _templates = templates; _renderer = renderer;
+        foreach (var template in templates.Store.GetTemplates()) Templates.Add(new(template));
+        SelectedTemplate = Templates.FirstOrDefault();
+        foreach (var id in studentIds)
+            if (students.GetById(id) is { } student) Students.Add(new(student));
+    }
+
+    public void Generate(string outputFolder)
+    {
+        Results.Clear();
+        if (SelectedTemplate is null) return;
+        LoadedTemplate loaded;
+        try { loaded = _templates.Store.Load(SelectedTemplate.Model); }
+        catch (Exception ex) when (ex is IOException or InvalidDataException or TemplateValidationException)
+        { StatusMessage = $"Vorlage ist ungültig: {ex.Message}"; return; }
+
+        Directory.CreateDirectory(outputFolder);
+        foreach (var choice in Students.Where(x => x.IsIncluded))
+        {
+            var student = choice.Model;
+            try
+            {
+                var values = LetterPlaceholderBuilder.BuildStandardValues(student, contact: null, _group,
+                    DateOnly.FromDateTime(DateTime.Now), "", "");
+                var pdf = _renderer.RenderToPdf(loaded, new LetterDataProvider(values));
+                var fileName = SanitizeFileName($"{SelectedTemplate.Name}_{student.LastName}_{student.FirstName}.pdf");
+                File.WriteAllBytes(Path.Combine(outputFolder, fileName), pdf);
+                Results.Add(new(student.FullName, true, ""));
+            }
+            catch (Exception ex) when (ex is IOException or InvalidDataException or UnauthorizedAccessException or TemplateValidationException)
+            { Results.Add(new(student.FullName, false, ex.Message)); }
+        }
+        OnPropertyChanged(nameof(HasResults));
+        StatusMessage = $"{Results.Count(x => x.Success)} von {Results.Count} Arbeitsblättern erzeugt.";
+    }
+
+    private static string SanitizeFileName(string value)
+    { foreach (var character in Path.GetInvalidFileNameChars()) value = value.Replace(character, '_'); return value; }
+}
+
+public partial class WorksheetStudentChoice(Student model) : ObservableObject
+{
+    public Student Model { get; } = model;
+    public string FullName => Model.FullName;
+    [ObservableProperty] private bool _isIncluded = true;
+}
+
+public sealed record WorksheetGenerationResult(string StudentName, bool Success, string ErrorMessage)
+{
+    public string Icon => Success ? "✓" : "⚠";
+    public string Color => Success ? "SeaGreen" : "#D97706";
+}

LehrerApp.Desktop/ViewModels/MainWindowViewModel.cs

@@ -12,6 +12,7 @@ using LehrerApp.Desktop.ViewModels.Students;
 using LehrerApp.Desktop.ViewModels.Workload;
 using Microsoft.Extensions.DependencyInjection;
 using System.Collections.ObjectModel;
+using System.ComponentModel;
 
 namespace LehrerApp.Desktop.ViewModels;
 
@@ -38,6 +39,9 @@ public partial class MainWindowViewModel : ObservableObject
     public bool IsClassTeacherActive => ActiveNavItem == NavItem.ClassTeacher;
     public bool IsSettingsActive  => ActiveNavItem == NavItem.Settings;
 
+    public GroupDetailViewModel? CurrentGroupDetail => CurrentPage as GroupDetailViewModel;
+    public bool CanPersonalizeWorksheet => CurrentGroupDetail?.Group is not null;
+
     public MainWindowViewModel(IServiceProvider services,
         DashboardViewModel dashboard, SchoolYearService sy,
         SyncStatusViewModel syncStatus, NotificationService notifications, AppLockViewModel appLock,
@@ -103,6 +107,25 @@ public partial class MainWindowViewModel : ObservableObject
         }
     }
 
+    // GroupDetailViewModel.Group wird erst nach dem Wechsel von CurrentPage per LoadGroup gesetzt
+    // (siehe Kommentar in NavigateToGroupDetail) - ohne dieses Abonnement bliebe
+    // CanPersonalizeWorksheet bis zum nächsten Seitenwechsel auf dem alten Stand.
+    private GroupDetailViewModel? _observedGroupDetail;
+
+    partial void OnCurrentPageChanged(ObservableObject? value)
+    {
+        if (_observedGroupDetail is not null) _observedGroupDetail.PropertyChanged -= OnGroupDetailPropertyChanged;
+        _observedGroupDetail = value as GroupDetailViewModel;
+        if (_observedGroupDetail is not null) _observedGroupDetail.PropertyChanged += OnGroupDetailPropertyChanged;
+        OnPropertyChanged(nameof(CurrentGroupDetail));
+        OnPropertyChanged(nameof(CanPersonalizeWorksheet));
+    }
+
+    private void OnGroupDetailPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName == nameof(GroupDetailViewModel.Group)) OnPropertyChanged(nameof(CanPersonalizeWorksheet));
+    }
+
     partial void OnActiveNavItemChanged(NavItem value)
     {
         OnPropertyChanged(nameof(IsDashboardActive));

LehrerApp.Desktop/ViewModels/Settings/SettingsViewModel.WorksheetTemplates.cs

@@ -0,0 +1,60 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using LehrerApp.Templating;
+using System.Collections.ObjectModel;
+
+namespace LehrerApp.Desktop.ViewModels.Settings;
+
+public partial class SettingsViewModel
+{
+    [ObservableProperty] private string _worksheetTemplateStatus = "";
+    public ObservableCollection<LetterTemplateListItem> WorksheetTemplateList { get; } = [];
+
+    private void LoadWorksheetTemplates()
+    {
+        WorksheetTemplateList.Clear();
+        foreach (var template in _worksheetTemplates.Store.GetTemplates()) WorksheetTemplateList.Add(CreateWorksheetItem(template));
+    }
+
+    public void ImportWorksheetTemplate(string path)
+    {
+        WorksheetTemplateStatus = "";
+        try
+        {
+            var template = _worksheetTemplates.Store.Import(path);
+            LoadWorksheetTemplates();
+            WorksheetTemplateStatus = $"„{template.Name}“ wurde geprüft und lokal importiert.";
+        }
+        catch (Exception ex) when (ex is IOException or InvalidDataException or UnauthorizedAccessException or TemplateValidationException)
+        { WorksheetTemplateStatus = $"Import fehlgeschlagen: {ex.Message}"; }
+    }
+
+    [RelayCommand]
+    private void ValidateWorksheetTemplate(LetterTemplateListItem? item)
+    {
+        if (item is null) return;
+        try
+        {
+            var refreshed = CreateWorksheetItem(item.Model);
+            var index = WorksheetTemplateList.IndexOf(item);
+            if (index >= 0) WorksheetTemplateList[index] = refreshed;
+            WorksheetTemplateStatus = $"„{item.Name}“ ist gültig (Schema {refreshed.SchemaVersion}).";
+        }
+        catch (Exception ex) when (ex is IOException or InvalidDataException or TemplateValidationException)
+        { WorksheetTemplateStatus = $"„{item.Name}“ ist ungültig: {ex.Message}"; }
+    }
+
+    [RelayCommand]
+    private void DeleteWorksheetTemplate(LetterTemplateListItem? item)
+    {
+        if (item is null) return;
+        _worksheetTemplates.Store.Delete(item.Id); WorksheetTemplateList.Remove(item); WorksheetTemplateStatus = "Vorlage gelöscht.";
+    }
+
+    private LetterTemplateListItem CreateWorksheetItem(InstalledTemplate template)
+    {
+        var loaded = _worksheetTemplates.Store.Load(template);
+        return new(template, loaded.Manifest.SchemaVersion, loaded.Manifest.Placeholders.Count(x => !x.IsConstant),
+            loaded.Manifest.Placeholders.Count(x => !x.IsConstant && x.Required));
+    }
+}

LehrerApp.Desktop/ViewModels/Settings/SettingsViewModel.cs

@@ -62,6 +62,7 @@ public partial class SettingsViewModel : ObservableObject
     private readonly IStudentRepository _students;
     private readonly IShorthandCodeRepository _shorthandCodes;
     private readonly TemplateStore _letterTemplates;
+    private readonly WorksheetTemplateStore _worksheetTemplates;
 
     [ObservableProperty] private int _activeTabIndex;
 
@@ -102,6 +103,7 @@ public partial class SettingsViewModel : ObservableObject
         IShorthandCodeRepository shorthandCodes, ISchoolHolidayRepository schoolHolidays,
         SchoolCalendarSettingsService calendarSettings, PeriodScheduleService periodSchedule,
         ISupervisionDutyRepository supervisionDuties, TemplateStore letterTemplates,
+        WorksheetTemplateStore worksheetTemplates,
         AiSettingsService aiSettings, AiPlanningService aiPlanning, McpSettingsService mcpSettings,
         Services.Mcp.McpClientRegistrationService mcpRegistration,
         WebUntisSettingsService untisSettings,
@@ -139,6 +141,7 @@ public partial class SettingsViewModel : ObservableObject
         _periodSchedule = periodSchedule;
         _supervisionDuties = supervisionDuties;
         _letterTemplates = letterTemplates;
+        _worksheetTemplates = worksheetTemplates;
         _aiSettings = aiSettings;
         _aiPlanning = aiPlanning;
         _mcpSettings = mcpSettings;
@@ -169,6 +172,7 @@ public partial class SettingsViewModel : ObservableObject
         LoadPeriodTimes();
         LoadSupervisionDuties();
         LoadLetterTemplates();
+        LoadWorksheetTemplates();
         LoadAiSettings();
         LoadMcpSettings();
         LoadMcpRegistrationStatus();

LehrerApp.Desktop/ViewModels/Students/StudentPickerDialogViewModel.cs

@@ -0,0 +1,48 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using LehrerApp.Core.Interfaces;
+using LehrerApp.Core.Models;
+using LehrerApp.Desktop.ViewModels.Groups;
+using System.Collections.ObjectModel;
+
+namespace LehrerApp.Desktop.ViewModels.Students;
+
+/// <summary>Einfacher "einen Schüler wählen"-Dialog für Einstiegspunkte ohne bereits geöffneten
+/// Schüler (z.B. das Formulare-Menü) - anders als <see cref="Groups.AddStudentToGroupDialogViewModel"/>
+/// ohne Gruppenbezug/Mitgliedschaftszeitraum, einfach alle Schüler durchsuchbar.</summary>
+public partial class StudentPickerDialogViewModel : ObservableObject
+{
+    private readonly IStudentRepository _students;
+
+    [ObservableProperty] private string _searchText = "";
+    [ObservableProperty] private StudentPickerItem? _selectedStudent;
+    [ObservableProperty] private string _validationMessage = "";
+
+    public ObservableCollection<StudentPickerItem> Students { get; } = [];
+    public Student? Result { get; private set; }
+
+    public StudentPickerDialogViewModel(IStudentRepository students)
+    {
+        _students = students;
+        LoadStudents();
+    }
+
+    partial void OnSearchTextChanged(string value) => LoadStudents();
+
+    private void LoadStudents()
+    {
+        var matches = _students.GetAll()
+            .Where(s => string.IsNullOrWhiteSpace(SearchText) ||
+                        s.FullName.Contains(SearchText, StringComparison.OrdinalIgnoreCase))
+            .OrderBy(s => s.FullName, StringComparer.CurrentCultureIgnoreCase);
+        Students.Clear();
+        foreach (var student in matches) Students.Add(new StudentPickerItem(student));
+    }
+
+    [RelayCommand]
+    private void Select()
+    {
+        if (SelectedStudent is null) { ValidationMessage = "Bitte einen Schüler auswählen."; return; }
+        Result = _students.GetById(SelectedStudent.Id);
+    }
+}