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/websocket_routes.py

@@ -0,0 +1,143 @@
+"""
+Classroom API - WebSocket Routes
+
+Real-time WebSocket endpoints for timer updates.
+"""
+
+import json
+from typing import Dict, Any
+from datetime import datetime
+import logging
+
+from fastapi import APIRouter, WebSocket, WebSocketDisconnect
+
+from ..services.persistence import (
+    sessions,
+    init_db_if_needed,
+    DB_ENABLED,
+    SessionLocal,
+)
+from ..websocket_manager import (
+    ws_manager,
+    start_timer_broadcast,
+    build_timer_status,
+    is_timer_broadcast_running,
+)
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(tags=["WebSocket"])
+
+
+@router.websocket("/ws/{session_id}")
+async def websocket_timer(websocket: WebSocket, session_id: str):
+    """
+    WebSocket-Endpoint fuer Echtzeit-Timer-Updates.
+
+    Features:
+    - Sub-Sekunden Timer-Updates (jede Sekunde)
+    - Phasenwechsel-Benachrichtigungen
+    - Session-Ende-Benachrichtigungen
+    - Multi-Device Support
+
+    Protocol:
+    - Server sendet JSON-Messages mit "type" und "data"
+    - Types: "timer_update", "phase_change", "session_ended", "error", "connected"
+    - Client kann "ping" senden fuer Keepalive
+    """
+    # Session validieren bevor Connect
+    session = sessions.get(session_id)
+    if not session:
+        # Versuche aus DB zu laden
+        if DB_ENABLED:
+            try:
+                init_db_if_needed()
+                from classroom_engine.repository import SessionRepository
+                db = SessionLocal()
+                repo = SessionRepository(db)
+                db_session = repo.get_by_id(session_id)
+                if db_session:
+                    session = repo.to_dataclass(db_session)
+                    sessions[session_id] = session
+                db.close()
+            except Exception as e:
+                logger.error(f"WebSocket: Failed to load session {session_id}: {e}")
+
+    if not session:
+        await websocket.close(code=4004, reason="Session not found")
+        return
+
+    if session.is_ended:
+        await websocket.close(code=4001, reason="Session already ended")
+        return
+
+    # Verbindung akzeptieren und registrieren
+    await ws_manager.connect(websocket, session_id)
+
+    # Timer-Broadcast-Task starten wenn noetig
+    start_timer_broadcast(sessions)
+
+    # Initiale Daten senden
+    try:
+        initial_timer = build_timer_status(session)
+        await websocket.send_json({
+            "type": "connected",
+            "data": {
+                "session_id": session_id,
+                "client_count": ws_manager.get_client_count(session_id),
+                "timer": initial_timer
+            }
+        })
+    except Exception as e:
+        logger.error(f"WebSocket: Failed to send initial data: {e}")
+
+    # Message-Loop
+    try:
+        while True:
+            try:
+                message = await websocket.receive_text()
+                data = json.loads(message)
+
+                if data.get("type") == "ping":
+                    await websocket.send_json({"type": "pong"})
+                elif data.get("type") == "get_timer":
+                    # Client kann manuell Timer-Status anfordern
+                    session = sessions.get(session_id)
+                    if session and not session.is_ended:
+                        timer_data = build_timer_status(session)
+                        await websocket.send_json({
+                            "type": "timer_update",
+                            "data": timer_data
+                        })
+            except json.JSONDecodeError:
+                await websocket.send_json({
+                    "type": "error",
+                    "data": {"message": "Invalid JSON"}
+                })
+    except WebSocketDisconnect:
+        logger.info(f"WebSocket: Client disconnected from session {session_id}")
+    except Exception as e:
+        logger.error(f"WebSocket error: {e}")
+    finally:
+        await ws_manager.disconnect(websocket)
+
+
+@router.get("/ws/status")
+async def websocket_status() -> Dict[str, Any]:
+    """
+    Status-Endpoint fuer WebSocket-Verbindungen.
+
+    Zeigt aktive Sessions und Verbindungszahlen.
+    """
+    active_sessions = ws_manager.get_active_sessions()
+    return {
+        "active_sessions": len(active_sessions),
+        "sessions": [
+            {
+                "session_id": sid,
+                "client_count": ws_manager.get_client_count(sid)
+            }
+            for sid in active_sessions
+        ],
+        "broadcast_task_running": is_timer_broadcast_running()
+    }