Notenverwaltung (Kapitel 2) und Mitarbeits-Assistent

Notenübersicht der Gruppe (Matrix, Gesamt-Spalte, Sortierung, Halbjahresfilter),
Einzelnoten-Pflege samt Sammelerfassung, Gewichtungsschema mit Voreinstellung je
Gruppentyp, Zeugnisnoten-Berechnung mit Übersteuern/Festschreiben/Export und
Notenentwicklung im Schülerdetail.

Dazu Anwesenheits-/Hausaufgaben-Tracking je Mitarbeit-Sitzung, ein neuer
Mitarbeits-Assistent (Zeitleiste mit Abschnitten, automatischer Notenvorschlag,
Zusammenzug zur Halbjahresnote) und eine Dashboard-Kachel für offene
Entschuldigungen. Außerdem: verbliebene englische Begriffe in Auswahlfeldern
und Buttons auf Deutsch umgestellt.

LehrerApp.Desktop/ViewModels/DashboardViewModel.cs

@@ -17,8 +17,13 @@ public partial class DashboardViewModel : ObservableObject
     private readonly ILessonRepository _lessons;
     private readonly IExamRepository _exams;
     private readonly IWorkTaskRepository _tasks;
+    private readonly IParticipationSessionRepository _participationSessions;
+    private readonly IParticipationRepository _participationEntries;
+    private readonly IStudentRepository _students;
     private readonly SchoolYearService _sy;
 
+    private const int OpenExcuseMaxAgeDays = 21;
+
     [ObservableProperty] private string _greeting = "";
     [ObservableProperty] private string _currentDate = "";
     [ObservableProperty] private string _currentSchoolYear = "";
@@ -30,15 +35,19 @@ public partial class DashboardViewModel : ObservableObject
     public ObservableCollection<TaskItem> OpenTasks { get; } = [];
     public ObservableCollection<GroupChip> CurrentGroups { get; } = [];
     public ObservableCollection<CalendarDayCell> CalendarDays { get; } = [];
+    public ObservableCollection<OpenExcuseItem> OpenExcuses { get; } = [];
     public static string[] CalendarWeekdayHeaders { get; } = ["Mo", "Di", "Mi", "Do", "Fr", "Sa", "So"];
 
     // Navigation-Callback – wird von App.axaml.cs verdrahtet
     public Action<Guid>? OnNavigateToGroup { get; set; }
 
     public DashboardViewModel(IGroupRepository groups, ISubjectRepository subjects, ILessonRepository lessons,
-        IExamRepository exams, IWorkTaskRepository tasks, SchoolYearService sy)
+        IExamRepository exams, IWorkTaskRepository tasks, IParticipationSessionRepository participationSessions,
+        IParticipationRepository participationEntries, IStudentRepository students, SchoolYearService sy)
     {
-        _groups = groups; _subjects = subjects; _lessons = lessons; _exams = exams; _tasks = tasks; _sy = sy;
+        _groups = groups; _subjects = subjects; _lessons = lessons; _exams = exams; _tasks = tasks;
+        _participationSessions = participationSessions; _participationEntries = participationEntries;
+        _students = students; _sy = sy;
         Load();
     }
 
@@ -80,6 +89,41 @@ public partial class DashboardViewModel : ObservableObject
 
         CalendarMonth = FirstOfMonth(now);
         LoadCalendar();
+        LoadOpenExcuses(groups.Values.ToList(), today);
+    }
+
+    private void LoadOpenExcuses(List<LearningGroup> groups, DateOnly today)
+    {
+        OpenExcuses.Clear();
+        var cutoff = today.AddDays(-OpenExcuseMaxAgeDays);
+
+        var items = new List<OpenExcuseItem>();
+        foreach (var g in groups)
+        {
+            foreach (var session in _participationSessions.GetByGroup(g.Id).Where(s => s.Date >= cutoff && s.Date <= today))
+            {
+                foreach (var entry in _participationEntries.GetBySession(session.Id)
+                             .Where(e => e.Attendance == AttendanceStatus.ExcusePending))
+                {
+                    var student = _students.GetById(entry.StudentId);
+                    if (student is null) continue;
+                    var item = new OpenExcuseItem(session.Id, entry.StudentId, student.FullName, g.Name, session.Date);
+                    item.OnResolve = ResolveExcuse;
+                    items.Add(item);
+                }
+            }
+        }
+        foreach (var item in items.OrderBy(i => i.Date))
+            OpenExcuses.Add(item);
+    }
+
+    private void ResolveExcuse(OpenExcuseItem item, AttendanceStatus status)
+    {
+        var entry = _participationEntries.GetBySessionAndStudent(item.SessionId, item.StudentId);
+        if (entry is null) return;
+        entry.Attendance = status;
+        _participationEntries.Save(entry);
+        OpenExcuses.Remove(item);
     }
 
     private void LoadCalendar()
@@ -172,6 +216,33 @@ public class LessonItem { public string GroupName { get; set; } = ""; public str
 public class TaskItem   { public string Title { get; set; } = ""; public string DueDate { get; set; } = ""; public bool IsOverdue { get; set; } }
 public class GroupChip  { public Guid GroupId { get; set; } public string Name { get; set; } = ""; public string Subject { get; set; } = ""; }
 
+// ── Offene Entschuldigungen (aus Mitarbeit-Fehltagen) ────────────────────────
+
+public partial class OpenExcuseItem : ObservableObject
+{
+    public Guid SessionId { get; }
+    public Guid StudentId { get; }
+    public string StudentName { get; }
+    public string GroupName { get; }
+    public DateOnly Date { get; }
+    public string DateDisplay { get; }
+
+    public Action<OpenExcuseItem, AttendanceStatus>? OnResolve { get; set; }
+
+    public OpenExcuseItem(Guid sessionId, Guid studentId, string studentName, string groupName, DateOnly date)
+    {
+        SessionId = sessionId;
+        StudentId = studentId;
+        StudentName = studentName;
+        GroupName = groupName;
+        Date = date;
+        DateDisplay = date.ToString("dd.MM.yyyy");
+    }
+
+    [RelayCommand] private void MarkExcused()   => OnResolve?.Invoke(this, AttendanceStatus.Excused);
+    [RelayCommand] private void MarkUnexcused() => OnResolve?.Invoke(this, AttendanceStatus.Unexcused);
+}
+
 public class CalendarDayCell
 {
     public int DayNumber { get; }