fix(ws): close registry pubsub connection on shutdown

Track the registry_pubsub connection and close it in the finally block
to prevent Redis connection leaks on WebSocket server shutdown.

autogpt_platform/backend/backend/api/ws_api.py

@@ -79,19 +79,23 @@ async def event_broadcaster(manager: ConnectionManager):
                     payload=notification.payload,
                 )
 
+        # Track registry pubsub for cleanup
+        registry_pubsub = None
+
         async def registry_refresh_worker():
             """Listen for LLM registry refresh notifications and broadcast to all clients."""
+            nonlocal registry_pubsub
             from backend.data.llm_registry import REGISTRY_REFRESH_CHANNEL
             from backend.data.redis_client import connect_async
 
             redis = await connect_async()
-            pubsub = redis.pubsub()
-            await pubsub.subscribe(REGISTRY_REFRESH_CHANNEL)
+            registry_pubsub = redis.pubsub()
+            await registry_pubsub.subscribe(REGISTRY_REFRESH_CHANNEL)
             logger.info(
                 "Subscribed to LLM registry refresh notifications for WebSocket broadcast"
             )
 
-            async for message in pubsub.listen():
+            async for message in registry_pubsub.listen():
                 if (
                     message["type"] == "message"
                     and message["channel"] == REGISTRY_REFRESH_CHANNEL
@@ -116,6 +120,8 @@ async def event_broadcaster(manager: ConnectionManager):
         # Ensure PubSub connections are closed on any exit to prevent leaks
         await execution_bus.close()
         await notification_bus.close()
+        if registry_pubsub:
+            await registry_pubsub.close()
 
 
 async def authenticate_websocket(websocket: WebSocket) -> str: