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_api.py

@@ -0,0 +1,84 @@
+"""
+Classroom API - Legacy Import Wrapper
+
+This file provides backward compatibility for code that imports from classroom_api.
+All functionality has been moved to the classroom/ module.
+
+Usage (new):
+    from classroom import router as classroom_router
+
+Usage (legacy, still works):
+    from classroom_api import router
+"""
+
+# Re-export everything from the new modular structure
+from classroom import (
+    # 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,
+)
+
+# For any direct imports of internal components
+from classroom.services.persistence import (
+    get_session_or_404,
+    persist_session,
+    SessionLocal,
+)
+
+from classroom.routes.sessions import build_session_response
+
+__all__ = [
+    "router",
+    "sessions",
+    "init_db_if_needed",
+    "DB_ENABLED",
+    "ws_manager",
+    "notify_phase_change",
+    "notify_session_ended",
+    "CreateSessionRequest",
+    "SessionResponse",
+    "TimerStatus",
+    "TemplateCreate",
+    "TemplateResponse",
+    "CreateHomeworkRequest",
+    "HomeworkResponse",
+    "CreateMaterialRequest",
+    "MaterialResponse",
+    "SessionSummaryResponse",
+    "TeacherAnalyticsResponse",
+    "ReflectionCreate",
+    "ReflectionResponse",
+    "FeedbackCreate",
+    "FeedbackResponse",
+    "TeacherSettingsResponse",
+    "TeacherContextResponse",
+    "get_session_or_404",
+    "persist_session",
+    "SessionLocal",
+    "build_session_response",
+]