feat: add MQTT integration for real-time entity updates

- aiomqtt async client with auto-reconnect and topic store
- MQTT router: GET /api/mqtt, GET /api/mqtt/topic/{path}, POST /api/mqtt/publish
- MQTT entities included in /api/all + WebSocket broadcast
- MqttCard frontend component with category filters, entity list
- Configurable via ENV: MQTT_HOST, MQTT_PORT, MQTT_USERNAME,
  MQTT_PASSWORD, MQTT_TOPICS (comma-separated or JSON array)
- Gracefully disabled when MQTT_HOST is not set

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/mockData.ts

@@ -146,6 +146,17 @@ export const MOCK_DATA: DashboardData = {
     lights_on: 3,
     lights_total: 8,
   },
+  mqtt: {
+    connected: true,
+    entities: [
+      { topic: "unraid/daddelolymp/cpu_temp", value: 52, timestamp: Date.now() / 1000 - 5, name: "Cpu Temp", category: "unraid" },
+      { topic: "unraid/daddelolymp/array_status", value: "normal", timestamp: Date.now() / 1000 - 12, name: "Array Status", category: "unraid" },
+      { topic: "unraid/moneyboy/cpu_temp", value: 41, timestamp: Date.now() / 1000 - 8, name: "Cpu Temp", category: "unraid" },
+      { topic: "zigbee2mqtt/wohnzimmer/temperature", value: 21.5, timestamp: Date.now() / 1000 - 30, name: "Temperature", category: "zigbee2mqtt" },
+      { topic: "zigbee2mqtt/wohnzimmer/humidity", value: 48, timestamp: Date.now() / 1000 - 30, name: "Humidity", category: "zigbee2mqtt" },
+      { topic: "frigate/events/front_door", value: "person", timestamp: Date.now() / 1000 - 120, name: "Front Door", category: "frigate" },
+    ],
+  },
   tasks: {
     private: {
       open: [