Remove unused import statement for sqlalchemy in main.py

backend/app/main.py

@@ -2423,8 +2423,6 @@ async def lifespan(app: FastAPI):
 
         # Restore MQTT smart plug subscriptions
         if mqtt_settings.get("mqtt_enabled"):
-            from sqlalchemy import select
-
             from backend.app.models.smart_plug import SmartPlug
 
             result = await db.execute(select(SmartPlug).where(SmartPlug.plug_type == "mqtt"))