fix: Restore all files lost during destructive rebase

A previous `git pull --rebase origin main` dropped 177 local commits,
losing 3400+ files across admin-v2, backend, studio-v2, website,
klausur-service, and many other services. The partial restore attempt
(660295e2) only recovered some files.

This commit restores all missing files from pre-rebase ref 98933f5e
while preserving post-rebase additions (night-scheduler, night-mode UI,
NightModeWidget dashboard integration).

Restored features include:
- AI Module Sidebar (FAB), OCR Labeling, OCR Compare
- GPU Dashboard, RAG Pipeline, Magic Help
- Klausur-Korrektur (8 files), Abitur-Archiv (5+ files)
- Companion, Zeugnisse-Crawler, Screen Flow
- Full backend, studio-v2, website, klausur-service
- All compliance SDKs, agent-core, voice-service
- CI/CD configs, documentation, scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/classroom/routes/settings.py

@@ -0,0 +1,184 @@
+"""
+Classroom API - Settings Routes
+
+Teacher settings endpoints (Feature f16).
+"""
+
+import logging
+
+from fastapi import APIRouter, HTTPException, Depends
+
+from classroom_engine import get_default_durations
+
+from ..models import (
+    TeacherSettingsResponse,
+    UpdatePhaseDurationsRequest,
+    UpdatePreferencesRequest,
+)
+from ..services.persistence import (
+    init_db_if_needed,
+    DB_ENABLED,
+    SessionLocal,
+)
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(tags=["Settings"])
+
+
+def get_db():
+    """Database session dependency."""
+    if DB_ENABLED and SessionLocal:
+        db = SessionLocal()
+        try:
+            yield db
+        finally:
+            db.close()
+    else:
+        yield None
+
+
+@router.get("/settings/{teacher_id}", response_model=TeacherSettingsResponse)
+async def get_teacher_settings(
+    teacher_id: str,
+    db=Depends(get_db)
+):
+    """
+    Holt die Einstellungen eines Lehrers.
+
+    Gibt die personalisierten Phasen-Dauern und UI-Praeferenzen zurueck.
+    Falls keine Einstellungen existieren, werden Defaults erstellt.
+
+    Args:
+        teacher_id: ID des Lehrers
+
+    Returns:
+        TeacherSettingsResponse mit allen Einstellungen
+    """
+    if DB_ENABLED and db:
+        try:
+            from classroom_engine.repository import TeacherSettingsRepository
+            repo = TeacherSettingsRepository(db)
+            settings = repo.get_or_create(teacher_id)
+            return TeacherSettingsResponse(
+                teacher_id=settings.teacher_id,
+                default_phase_durations=settings.default_phase_durations or get_default_durations(),
+                audio_enabled=settings.audio_enabled if settings.audio_enabled is not None else True,
+                high_contrast=settings.high_contrast if settings.high_contrast is not None else False,
+                show_statistics=settings.show_statistics if settings.show_statistics is not None else True,
+            )
+        except Exception as e:
+            logger.error(f"Failed to get teacher settings: {e}")
+            raise HTTPException(status_code=500, detail=f"Fehler beim Laden der Einstellungen: {e}")
+
+    # Fallback: Defaults
+    return TeacherSettingsResponse(
+        teacher_id=teacher_id,
+        default_phase_durations=get_default_durations(),
+        audio_enabled=True,
+        high_contrast=False,
+        show_statistics=True,
+    )
+
+
+@router.put("/settings/{teacher_id}/durations", response_model=TeacherSettingsResponse)
+async def update_phase_durations(
+    teacher_id: str,
+    request: UpdatePhaseDurationsRequest,
+    db=Depends(get_db)
+):
+    """
+    Aktualisiert die Standard-Phasendauern eines Lehrers.
+
+    Ermoeglicht Lehrern, ihre bevorzugten Phasen-Dauern zu speichern.
+    Diese werden dann bei neuen Sessions als Default verwendet.
+
+    Args:
+        teacher_id: ID des Lehrers
+        request: Neue Phasen-Dauern in Minuten
+
+    Returns:
+        Aktualisierte TeacherSettingsResponse
+    """
+    # Validierung: Nur gueltige Phasen erlauben
+    valid_phases = {"einstieg", "erarbeitung", "sicherung", "transfer", "reflexion"}
+    for phase in request.durations:
+        if phase not in valid_phases:
+            raise HTTPException(
+                status_code=400,
+                detail=f"Ungueltige Phase: {phase}. Erlaubt: {valid_phases}"
+            )
+        if request.durations[phase] < 1 or request.durations[phase] > 120:
+            raise HTTPException(
+                status_code=400,
+                detail=f"Phasen-Dauer muss zwischen 1 und 120 Minuten liegen"
+            )
+
+    if DB_ENABLED and db:
+        try:
+            from classroom_engine.repository import TeacherSettingsRepository
+            repo = TeacherSettingsRepository(db)
+            settings = repo.update_phase_durations(teacher_id, request.durations)
+            return TeacherSettingsResponse(
+                teacher_id=settings.teacher_id,
+                default_phase_durations=settings.default_phase_durations,
+                audio_enabled=settings.audio_enabled if settings.audio_enabled is not None else True,
+                high_contrast=settings.high_contrast if settings.high_contrast is not None else False,
+                show_statistics=settings.show_statistics if settings.show_statistics is not None else True,
+            )
+        except Exception as e:
+            logger.error(f"Failed to update phase durations: {e}")
+            raise HTTPException(status_code=500, detail=f"Fehler beim Speichern: {e}")
+
+    raise HTTPException(
+        status_code=503,
+        detail="Datenbank nicht verfuegbar - Einstellungen koennen nicht gespeichert werden"
+    )
+
+
+@router.put("/settings/{teacher_id}/preferences", response_model=TeacherSettingsResponse)
+async def update_preferences(
+    teacher_id: str,
+    request: UpdatePreferencesRequest,
+    db=Depends(get_db)
+):
+    """
+    Aktualisiert die UI-Praeferenzen eines Lehrers.
+
+    Ermoeglicht das Speichern von:
+    - audio_enabled: Audio-Hinweise aktiviert
+    - high_contrast: Hoher Kontrast fuer Beamer
+    - show_statistics: Statistiken nach Stundenende anzeigen
+
+    Args:
+        teacher_id: ID des Lehrers
+        request: Zu aktualisierende Praeferenzen
+
+    Returns:
+        Aktualisierte TeacherSettingsResponse
+    """
+    if DB_ENABLED and db:
+        try:
+            from classroom_engine.repository import TeacherSettingsRepository
+            repo = TeacherSettingsRepository(db)
+            settings = repo.update_preferences(
+                teacher_id=teacher_id,
+                audio_enabled=request.audio_enabled,
+                high_contrast=request.high_contrast,
+                show_statistics=request.show_statistics
+            )
+            return TeacherSettingsResponse(
+                teacher_id=settings.teacher_id,
+                default_phase_durations=settings.default_phase_durations or get_default_durations(),
+                audio_enabled=settings.audio_enabled if settings.audio_enabled is not None else True,
+                high_contrast=settings.high_contrast if settings.high_contrast is not None else False,
+                show_statistics=settings.show_statistics if settings.show_statistics is not None else True,
+            )
+        except Exception as e:
+            logger.error(f"Failed to update preferences: {e}")
+            raise HTTPException(status_code=500, detail=f"Fehler beim Speichern: {e}")
+
+    raise HTTPException(
+        status_code=503,
+        detail="Datenbank nicht verfuegbar - Einstellungen koennen nicht gespeichert werden"
+    )