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/__init__.py

@@ -0,0 +1,110 @@
+"""
+Classroom API Module
+
+A modular classroom management API for lesson sessions, templates,
+homework, materials, analytics, and real-time features.
+
+Usage:
+    from classroom import router as classroom_router
+    app.include_router(classroom_router, prefix="/api/classroom")
+"""
+
+from fastapi import APIRouter
+
+from .routes.sessions import router as sessions_router
+from .routes.templates import router as templates_router
+from .routes.homework import router as homework_router
+from .routes.materials import router as materials_router
+from .routes.analytics import router as analytics_router
+from .routes.export import router as export_router
+from .routes.feedback import router as feedback_router
+from .routes.settings import router as settings_router
+from .routes.context import router as context_router
+from .routes.websocket_routes import router as websocket_router
+
+# Create the main router that combines all sub-routers
+router = APIRouter()
+
+# Include all sub-routers
+router.include_router(sessions_router)
+router.include_router(templates_router)
+router.include_router(homework_router)
+router.include_router(materials_router)
+router.include_router(analytics_router)
+router.include_router(export_router)
+router.include_router(feedback_router)
+router.include_router(settings_router)
+router.include_router(context_router)
+router.include_router(websocket_router)
+
+# Re-export commonly used items
+from .models import (
+    # Session Models
+    CreateSessionRequest,
+    SessionResponse,
+    TimerStatus,
+    # Template Models
+    TemplateCreate,
+    TemplateResponse,
+    # Homework Models
+    CreateHomeworkRequest,
+    HomeworkResponse,
+    # Material Models
+    CreateMaterialRequest,
+    MaterialResponse,
+    # Analytics Models
+    SessionSummaryResponse,
+    TeacherAnalyticsResponse,
+    ReflectionCreate,
+    ReflectionResponse,
+    # Feedback Models
+    FeedbackCreate,
+    FeedbackResponse,
+    # Settings Models
+    TeacherSettingsResponse,
+    # Context Models
+    TeacherContextResponse,
+)
+
+from .services.persistence import (
+    sessions,
+    init_db_if_needed,
+    DB_ENABLED,
+)
+
+from .websocket_manager import (
+    ws_manager,
+    notify_phase_change,
+    notify_session_ended,
+)
+
+__all__ = [
+    # Main router
+    "router",
+    # Session storage
+    "sessions",
+    "init_db_if_needed",
+    "DB_ENABLED",
+    # WebSocket
+    "ws_manager",
+    "notify_phase_change",
+    "notify_session_ended",
+    # Models
+    "CreateSessionRequest",
+    "SessionResponse",
+    "TimerStatus",
+    "TemplateCreate",
+    "TemplateResponse",
+    "CreateHomeworkRequest",
+    "HomeworkResponse",
+    "CreateMaterialRequest",
+    "MaterialResponse",
+    "SessionSummaryResponse",
+    "TeacherAnalyticsResponse",
+    "ReflectionCreate",
+    "ReflectionResponse",
+    "FeedbackCreate",
+    "FeedbackResponse",
+    "TeacherSettingsResponse",
+    "TeacherContextResponse",
+]