fix(mqtt): 修复 MQTT 连接反复断开重连的问题

- 协议从 MQTTv5 降级为 MQTTv311，提高兼容性
- client_id 添加随机后缀，防止多实例冲突导致互相踢连接
- 修复 on_connect/on_disconnect 回调的参数解析逻辑

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

app/services/mqtt_service.py

@@ -4,6 +4,7 @@ MQTT 订阅服务
 """
 import json
 import threading
+import uuid
 from datetime import datetime, timezone
 from typing import Callable, Dict, Any, Optional, List
 
@@ -59,20 +60,23 @@ class MQTTService:
             return
 
         try:
+            # 给 client_id 添加随机后缀，防止多实例 client_id 冲突导致反复踢连接
+            unique_client_id = f"{settings.mqtt.client_id}_{uuid.uuid4().hex[:8]}"
+
             # 兼容 paho-mqtt 1.x 和 2.x 版本
             try:
                 # paho-mqtt 2.0+ 新 API
                 self._client = mqtt.Client(
-                    client_id=settings.mqtt.client_id,
-                    protocol=mqtt.MQTTv5,
+                    client_id=unique_client_id,
+                    protocol=mqtt.MQTTv311,
                     callback_api_version=mqtt.CallbackAPIVersion.VERSION2
                 )
                 self._use_v2_callback = True
             except AttributeError:
                 # paho-mqtt 1.x 旧 API
                 self._client = mqtt.Client(
-                    client_id=settings.mqtt.client_id,
-                    protocol=mqtt.MQTTv5
+                    client_id=unique_client_id,
+                    protocol=mqtt.MQTTv311
                 )
                 self._use_v2_callback = False
                 logger.info("使用 paho-mqtt 1.x 兼容模式")
@@ -124,11 +128,14 @@ class MQTTService:
         """连接回调 (兼容 1.x 和 2.x)"""
         # 1.x: (client, userdata, flags, rc)
         # 2.x: (client, userdata, connect_flags, reason_code, properties)
+        rc = 0
         if args:
-            reason_code = args[-2] if len(args) >= 2 else args[-1]
-            rc = reason_code if isinstance(reason_code, int) else getattr(reason_code, 'value', reason_code)
+            # 取倒数第二个参数（1.x 的 rc 或 2.x 的 reason_code）
+            if len(args) >= 2:
+                reason_code = args[-2]
             else:
-            rc = -1
+                reason_code = args[0]
+            rc = reason_code if isinstance(reason_code, int) else getattr(reason_code, 'value', 0)
 
         if rc == 0:
             self._connected = True
@@ -149,12 +156,17 @@ class MQTTService:
         # 1.x: (client, userdata, rc)
         # 2.x: (client, userdata, disconnect_flags, reason_code, properties)
         self._connected = False
+        rc = 0
         if args:
-            reason_code = args[-2] if len(args) >= 2 else args[0]
-            rc = reason_code if isinstance(reason_code, int) else getattr(reason_code, 'value', reason_code)
-            logger.warning(f"MQTT 连接断开: {rc}")
+            if len(args) >= 2:
+                reason_code = args[-2]
             else:
-            logger.warning("MQTT 连接断开")
+                reason_code = args[0]
+            rc = reason_code if isinstance(reason_code, int) else getattr(reason_code, 'value', 0)
+        if rc != 0:
+            logger.warning(f"MQTT 连接异常断开: rc={rc}")
+        else:
+            logger.info("MQTT 连接断开")
 
     def _on_message(self, client, userdata, msg: mqtt.MQTTMessage):
         """消息回调"""