MQTT-FIX-T01: make main MQTT client lifecycle idempotent

app/main.py

@@ -169,9 +169,12 @@ def _run_scheduled_ha_state_publish() -> None:
     session: Session = session_local()
     try:
         runtime_settings = build_runtime_settings(session, get_settings())
-        # Reconnect if MQTT is configured (in DB) but not yet connected.
-        if mqtt_manager.is_configured(runtime_settings) and not mqtt_manager.is_connected:
-            logger.info("_run_scheduled_ha_state_publish: MQTT configured but not connected — attempting connect.")
+        # Ensure the configured MQTT client is installed; the manager avoids
+        # replacing it while Paho is already retrying a transient disconnect.
+        if mqtt_manager.is_configured(runtime_settings):
+            # connect() is idempotent for the same settings and retains a Paho
+            # client while its own loop is retrying a transient disconnect.
+            logger.info("_run_scheduled_ha_state_publish: ensuring MQTT client is active.")
             mqtt_manager.connect(runtime_settings)
         publish_discovery(session)
         publish_states(session)