fix: mqtt subscription format

- Updated MQTT subscription to use dict format with topic and qos
- Added better logging for MQTT connection status

backend/mqtt_integration.py

@@ -98,11 +98,13 @@ class HomeAssistantMQTT:
             self._reconnect_task = asyncio.create_task(self._reconnect_loop())
 
     async def _post_connect(self):
-        """Tasks to perform after connection is established"""
+        """Post connection setup - subscribe to topics"""
+        logger.info("Connected to MQTT broker")
+        self._connected = True
         try:
             # Subscribe to command topic
-            await self.client.subscribe([(self.command_topic, 1)])
-            logger.info(f"Subscribed to command topic: {self.command_topic}")
+            await self.client.subscribe([{'topic': self.command_topic, 'qos': 1}])
+            logger.info(f"Subscribed to {self.command_topic}")
             
             # Publish discovery config
             config = {