Baustein 2: Outbound-Hook-Infrastruktur (Kapitel 10)

LiteDbContext.OnChange-Hook (Sync-agnostisch, kein Verweis auf
LehrerApp.Sync aus LehrerApp.Data), damit Repositories lokale
Schreibvorgaenge signalisieren koennen, ohne dass Data von Sync
abhaengt. StudentRepository als Vorlage verdrahtet.

GroupRepository.Delete-Kaskade (14 betroffene Collections) nach
LiteDbContext.CascadeDeleteGroup extrahiert - reine Verschiebung,
kein Verhaltensunterschied, macht sie aber von einem spaeter
eingehenden Sync-Ereignis (Baustein 5) wiederverwendbar, ohne ueber
Repository-Save/Delete (und damit erneut ueber OnChange) zu laufen.

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

LehrerApp.Data/Repositories/AllRepositories.cs

@@ -35,7 +35,12 @@ public class StudentRepository(LiteDbContext db) : IStudentRepository
         db.ReportGrades.Count(g => g.StudentId == studentId),
         db.ParticipationEntries.Count(e => e.StudentId == studentId),
         db.Documentation.Count(d => d.StudentId == studentId));
-    public void Save(Student s) { s.UpdatedAt = DateTime.UtcNow; db.Students.Upsert(s); }
+    public void Save(Student s)
+    {
+        s.UpdatedAt = DateTime.UtcNow;
+        db.Students.Upsert(s);
+        db.OnChange?.Invoke(nameof(Student), s.Id.ToString(), "Save", s);
+    }
     public void Delete(Guid id)
     {
         var references = GetReferenceSummary(id);
@@ -43,6 +48,7 @@ public class StudentRepository(LiteDbContext db) : IStudentRepository
             throw new InvalidOperationException(
                 "Der Schüler besitzt verknüpfte Daten und kann nur deaktiviert werden.");
         db.Students.Delete(id);
+        db.OnChange?.Invoke(nameof(Student), id.ToString(), "Delete", null);
     }
 }
 
@@ -77,77 +83,7 @@ public class GroupRepository(LiteDbContext db) : IGroupRepository
     public void Delete(Guid id)
     {
         ArchivedGroupWriteGuard.EnsureActive(db, id);
-        db.ExecuteInTransaction(() =>
-        {
-            foreach (var membership in db.Memberships.Find(e => e.GroupId == id).ToList())
-                db.Memberships.Delete(membership.Id);
-
-            foreach (var exam in db.Exams.Find(e => e.GroupId == id).ToList())
-            {
-                foreach (var result in db.ExamResults.Find(r => r.ExamId == exam.Id).ToList())
-                    db.ExamResults.Delete(result.Id);
-                db.Exams.Delete(exam.Id);
-            }
-
-            foreach (var grade in db.Grades.Find(g => g.GroupId == id).ToList())
-                db.Grades.Delete(grade.Id);
-
-            foreach (var reportGrade in db.ReportGrades.Find(g => g.GroupId == id).ToList())
-                db.ReportGrades.Delete(reportGrade.Id);
-
-            foreach (var scheme in db.GradingSchemes.Find(s => s.GroupId == id).ToList())
-                db.GradingSchemes.Delete(scheme.Id);
-
-            foreach (var unit in db.Units.Find(u => u.GroupId == id).ToList())
-            {
-                foreach (var lesson in db.Lessons.Find(l => l.UnitId == unit.Id).ToList())
-                    db.Lessons.Delete(lesson.Id);
-                db.Units.Delete(unit.Id);
-            }
-
-            foreach (var lesson in db.Lessons.Find(l => l.GroupId == id).ToList())
-                db.Lessons.Delete(lesson.Id);
-
-            foreach (var session in db.ParticipationSessions.Find(s => s.GroupId == id).ToList())
-            {
-                foreach (var entry in db.ParticipationEntries.Find(e => e.SessionId == session.Id).ToList())
-                    db.ParticipationEntries.Delete(entry.Id);
-                db.ParticipationSessions.Delete(session.Id);
-            }
-
-            foreach (var aspect in db.ParticipationAspects.Find(a => a.GroupId == id).ToList())
-                db.ParticipationAspects.Delete(aspect.Id);
-
-            foreach (var section in db.ParticipationSections.Find(s => s.GroupId == id).ToList())
-                db.ParticipationSections.Delete(section.Id);
-
-            foreach (var plan in db.SeatingPlans.Find(p => p.GroupId == id).ToList())
-                db.SeatingPlans.Delete(plan.Id);
-
-            // Dokumentation und Arbeitszeit sind historische Nachweise. Sie bleiben erhalten,
-            // werden aber von der nicht mehr existierenden Lerngruppe entkoppelt.
-            foreach (var documentation in db.Documentation.Find(d => d.GroupId == id).ToList())
-            {
-                documentation.GroupId = null;
-                documentation.UpdatedAt = DateTime.UtcNow;
-                db.Documentation.Update(documentation);
-            }
-
-            foreach (var task in db.Tasks.Find(t => t.GroupId == id).ToList())
-            {
-                task.GroupId = null;
-                task.UpdatedAt = DateTime.UtcNow;
-                db.Tasks.Update(task);
-            }
-
-            foreach (var timeEntry in db.TimeEntries.Find(t => t.GroupId == id).ToList())
-            {
-                timeEntry.GroupId = null;
-                db.TimeEntries.Update(timeEntry);
-            }
-
-            db.Groups.Delete(id);
-        });
+        db.CascadeDeleteGroup(id);
     }
 }