fix: complete admin knowledge audit improvements

ai_knowledge_base_v2/apps/backend/app/main.py

@@ -11,6 +11,8 @@ from app.core.database import create_tables
 from app.core.exception_handlers import register_exception_handlers
 from app.core.observability import RequestObservabilityMiddleware, configure_logging
 from app.services.secret_service import SecretService
+from app.services.maintenance_service import MaintenanceService
+import asyncio
 
 
 @asynccontextmanager
@@ -19,7 +21,15 @@ async def lifespan(app: FastAPI):
     SecretService.validate_production_key()
     if settings.auto_create_tables:
         create_tables()
-    yield
+    maintenance_task = asyncio.create_task(MaintenanceService.run_forever())
+    try:
+        yield
+    finally:
+        maintenance_task.cancel()
+        try:
+            await maintenance_task
+        except asyncio.CancelledError:
+            pass
 
 
 settings = get_settings()