feat: refactor MQTT from global config to multi-instance entity model

MQTT broker connections are now managed as entities (like HA sources)
instead of a single global config. Each MQTTSource gets its own
runtime with auto-reconnect, ref-counted via MQTTManager.

Backend:
- MQTTSource dataclass + MQTTSourceStore (SQLite)
- MQTTRuntime (per-broker connection, refactored from MQTTService)
- MQTTManager (ref-counted pool, same pattern as HAManager)
- CRUD API at /api/v1/mqtt/sources + test + status endpoints
- MQTTRule gains mqtt_source_id field for source selection
- Automation engine acquires/releases MQTT runtimes automatically
- Legacy MQTTService kept for backward compat during transition

Frontend:
- MQTT source cards in Streams > Integrations tab
- Create/edit modal with test button
- Dashboard integration cards with health-dot indicators
- Removed MQTT tab from settings modal

server/src/wled_controller/main.py

@@ -49,6 +49,8 @@ from wled_controller.core.game_integration.event_bus import GameEventBus
 import wled_controller.core.game_integration.adapters  # noqa: F401 — register built-in adapters
 from wled_controller.core.game_integration.community_loader import register_community_adapters
 from wled_controller.core.mqtt.mqtt_service import MQTTService
+from wled_controller.core.mqtt.mqtt_manager import MQTTManager
+from wled_controller.storage.mqtt_source_store import MQTTSourceStore
 from wled_controller.core.devices.mqtt_client import set_mqtt_service
 from wled_controller.core.backup.auto_backup import AutoBackupEngine
 from wled_controller.core.processing.os_notification_listener import OsNotificationListener
@@ -101,6 +103,7 @@ sync_clock_manager = SyncClockManager(sync_clock_store)
 weather_manager = WeatherManager(weather_source_store)
 ha_store = HomeAssistantStore(db)
 ha_manager = HomeAssistantManager(ha_store)
+mqtt_source_store = MQTTSourceStore(db)
 game_integration_store = GameIntegrationStore(db)
 game_event_bus = GameEventBus()
 register_community_adapters()
@@ -158,11 +161,14 @@ async def lifespan(app: FastAPI):
         client_labels = ", ".join(config.auth.api_keys.keys())
         logger.info(f"Authorized clients: {client_labels}")
 
-    # Create MQTT service (shared broker connection)
+    # Create MQTT service (shared broker connection — legacy, used by MQTTLEDClient)
     mqtt_service = MQTTService(config.mqtt)
     set_mqtt_service(mqtt_service)
 
-    # Create automation engine (needs processor_manager + mqtt_service + stores for scene activation)
+    # Create MQTT manager (multi-source, ref-counted — new entity-based model)
+    mqtt_manager = MQTTManager(mqtt_source_store)
+
+    # Create automation engine (needs processor_manager + mqtt + stores for scene activation)
     automation_engine = AutomationEngine(
         automation_store,
         processor_manager,
@@ -171,6 +177,7 @@ async def lifespan(app: FastAPI):
         target_store=output_target_store,
         device_store=device_store,
         ha_manager=ha_manager,
+        mqtt_manager=mqtt_manager,
     )
 
     # Create auto-backup engine — derive paths from database location so that
@@ -222,6 +229,8 @@ async def lifespan(app: FastAPI):
         ha_manager=ha_manager,
         game_integration_store=game_integration_store,
         game_event_bus=game_event_bus,
+        mqtt_store=mqtt_source_store,
+        mqtt_manager=mqtt_manager,
     )
 
     # Register devices in processor manager for health monitoring
@@ -332,7 +341,13 @@ async def lifespan(app: FastAPI):
     except Exception as e:
         logger.error(f"Error stopping processors: {e}")
 
-    # Stop MQTT service
+    # Stop MQTT manager (entity-based broker connections)
+    try:
+        await mqtt_manager.shutdown()
+    except Exception as e:
+        logger.error(f"Error stopping MQTT manager: {e}")
+
+    # Stop MQTT service (legacy global connection)
     try:
         await mqtt_service.stop()
     except Exception as e: