implement automatic MQTT reconnection with 10s retry interval

- Fix connection state management: only set connected=True on successful connection
- Add automatic reconnection loop that retries every 10 seconds indefinitely
- Proper cleanup of reconnection thread on stop
- Enhanced disconnect logging with reason codes
- Thread-safe reconnection handling to avoid blocking main MQTT thread

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frigate/comms/mqtt.py

@@ -1,5 +1,6 @@
 import logging
 import threading
+import time
 from typing import Any, Callable
 
 import paho.mqtt.client as mqtt
@@ -18,6 +19,9 @@ class MqttClient(Communicator):
         self.config = config
         self.mqtt_config = config.mqtt
         self.connected = False
+        self._reconnect_thread = None
+        self._reconnect_delay = 10  # Retry every 10 seconds
+        self._stop_reconnect = False
 
     def subscribe(self, receiver: Callable) -> None:
         """Wrapper for allowing dispatcher to subscribe."""
@@ -38,7 +42,11 @@ class MqttClient(Communicator):
         )
 
     def stop(self) -> None:
-        self.client.disconnect()
+        self._stop_reconnect = True
+        if self._reconnect_thread and self._reconnect_thread.is_alive():
+            self._reconnect_thread.join(timeout=5)
+        if hasattr(self, 'client'):
+            self.client.disconnect()
 
     def _set_initial_topics(self) -> None:
         """Set initial state topics."""
@@ -176,6 +184,8 @@ class MqttClient(Communicator):
                     "Unable to connect to MQTT server: Connection refused. Error code: "
                     + reason_code.getName()
                 )
+            # Don't set connected = True on connection failure
+            return
 
         self.connected = True
         logger.debug("MQTT connected")
@@ -192,7 +202,20 @@ class MqttClient(Communicator):
     ) -> None:
         """Mqtt disconnection callback."""
         self.connected = False
-        logger.error("MQTT disconnected")
+        logger.error(f"MQTT disconnected (reason: {reason_code.getName()})")
+        
+        # Don't attempt reconnection if we're stopping or if it was a clean disconnect
+        if self._stop_reconnect or reason_code == 0:
+            return
+            
+        # Start reconnection in a separate thread to avoid blocking
+        if not self._reconnect_thread or not self._reconnect_thread.is_alive():
+            self._reconnect_thread = threading.Thread(
+                target=self._reconnect_loop,
+                name="mqtt-reconnect",
+                daemon=True
+            )
+            self._reconnect_thread.start()
 
     def _start(self) -> None:
         """Start mqtt client."""
@@ -281,3 +304,28 @@ class MqttClient(Communicator):
         except Exception as e:
             logger.error(f"Unable to connect to MQTT server: {e}")
             return
+
+    def _reconnect_loop(self) -> None:
+        """Handle MQTT reconnection, retrying every 10 seconds indefinitely."""
+        attempt = 0
+        while not self._stop_reconnect and not self.connected:
+            attempt += 1
+            
+            logger.debug(f"Will attempt MQTT reconnection in {self._reconnect_delay} seconds (attempt {attempt})")
+            
+            # Wait with ability to exit early if stopping
+            for _ in range(self._reconnect_delay):
+                if self._stop_reconnect:
+                    return
+                time.sleep(1)
+                
+            if self._stop_reconnect:
+                break
+                
+            try:
+                logger.debug(f"Attempting MQTT reconnection (attempt {attempt})...")
+                self.client.reconnect()
+                break  # Let the on_connect callback handle success
+            except Exception as e:
+                logger.error(f"MQTT reconnection attempt {attempt} failed: {e}")
+                # Continue the loop to retry