fix: use lifespan context manager instead of deprecated on_event for startup

dashboard/backend/main.py

@@ -10,6 +10,7 @@ from routers import docker_router, gitea, files, terminal, system, chat_summary,
 import auth_service as auth_module
 import config
 from rbac import require_page
+from contextlib import asynccontextmanager
 
 import asyncio
 import httpx
@@ -21,8 +22,40 @@ from config import TELEGRAM_BOT_TOKEN, TELEGRAM_CHAT_ID, CORS_ORIGINS, SECRET_KE
 
 _tz_cst = timezone(timedelta(hours=8))
 
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    # Startup
+    print("=== Application Startup ===")
+
+    # Initialize OPC database
+    from db import opc_db
+    try:
+        await opc_db.init_db()
+        print("OPC database initialized")
+    except Exception as e:
+        print(f"Failed to initialize OPC database: {e}")
+        import traceback
+        traceback.print_exc()
+
+    # Start agent executor service
+    from services import agent_executor
+    try:
+        asyncio.create_task(agent_executor.start_executor())
+        print("Agent executor service started")
+    except Exception as e:
+        print(f"Failed to start agent executor: {e}")
+        import traceback
+        traceback.print_exc()
+
+    asyncio.create_task(monitor_containers())
+
+    yield
+
+    # Shutdown
+    print("=== Application Shutdown ===")
+
 limiter = Limiter(key_func=get_remote_address)
-app = FastAPI(title="NAS Dashboard")
+app = FastAPI(title="NAS Dashboard", lifespan=lifespan)
 app.state.limiter = limiter
 
 app.add_middleware(
@@ -111,26 +144,6 @@ async def monitor_containers():
         
         await asyncio.sleep(60)
 
-@app.on_event("startup")
-async def startup_event():
-    # Initialize OPC database
-    from db import opc_db
-    try:
-        await opc_db.init_db()
-        logging.getLogger(__name__).info("OPC database initialized")
-    except Exception as e:
-        logging.getLogger(__name__).error("Failed to initialize OPC database: %s", e)
-
-    # Start agent executor service
-    from services import agent_executor
-    try:
-        asyncio.create_task(agent_executor.start_executor())
-        logging.getLogger(__name__).info("Agent executor service started")
-    except Exception as e:
-        logging.getLogger(__name__).error("Failed to start agent executor: %s", e)
-
-    asyncio.create_task(monitor_containers())
-
 @app.get("/api/health")
 async def health():
     return {"status": "ok"}