Phase 5: Notifications — WebSocket, APScheduler, AI tool, health review

Backend:
- Notification model + Alembic migration
- Notification service: CRUD, mark read, unread count, pending scheduled
- WebSocket manager singleton for real-time push
- WebSocket endpoint /ws/notifications with JWT auth via query param
- APScheduler integration: periodic notification sender (every 60s),
  daily proactive health review job (8 AM)
- AI tool: schedule_notification (immediate or scheduled)
- Health review worker: analyzes user memory via Claude, creates
  ai_generated notifications with WebSocket push

Frontend:
- Notification API client + Zustand store
- WebSocket hook with auto-reconnect (exponential backoff)
- Notification bell in header with unread count badge + dropdown
- Notifications page with type badges, mark read, mark all read
- WebSocket initialized in AppLayout for app-wide real-time updates
- Enabled notifications nav in sidebar
- English + Russian translations

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/main.py

@@ -13,8 +13,14 @@ async def lifespan(app: FastAPI):
 
     alembic_cfg = Config("alembic.ini")
     command.upgrade(alembic_cfg, "head")
+
+    from app.services.scheduler_service import start_scheduler, shutdown_scheduler
+    start_scheduler()
+
     yield
 
+    shutdown_scheduler()
+
 
 def create_app() -> FastAPI:
     app = FastAPI(