fix: DeviceManager 死锁 — threading.Lock 改为 RLock

根因: update_from_dev_info/update_loop_data/update_event/update_heartbeat
      在 with self._lock 块内调用 get_or_create(), 后者再次 with self._lock.
      Python threading.Lock 不可重入 → 永久阻塞 → GUI 无响应.

修复: self._lock = threading.RLock() (可重入锁)

清理: mqtt_client.py 移除 debug print 和未使用的 sys import

DBNMQTTool/dbn_mqtt_tool/device_manager.py

@@ -29,7 +29,7 @@ class DeviceManager:
 
     def __init__(self):
         self._devices: dict[str, DeviceInfo] = {}
-        self._lock = threading.Lock()
+        self._lock = threading.RLock()  # 可重入锁: update_xxx 内部调用 get_or_create
         self._callbacks: list[Callable] = []
 
     def on_change(self, callback: Callable):

DBNMQTTool/dbn_mqtt_tool/mqtt_client.py

@@ -3,7 +3,6 @@ MQTT 客户端封装
 """
 import json
 import time
-import sys
 import threading
 from typing import Callable, Optional
 from dataclasses import dataclass
@@ -123,13 +122,7 @@ class MqttClient:
         if not self._client or not self._connected:
             raise ConnectionError("MQTT 未连接")
         data = json.dumps(payload, ensure_ascii=False)
-        print(f"[MqttClient] publish topic={topic} qos={qos}", flush=True)
-        try:
-            info = self._client.publish(topic, data, qos=qos)
-            print(f"[MqttClient] publish done mid={info.mid}", flush=True)
-        except Exception as e:
-            print(f"[MqttClient] publish EXCEPTION: {e}", flush=True)
-            raise
+        self._client.publish(topic, data, qos=qos)
 
     def subscribe(self, topic: str, qos: int = 1):
         """订阅主题"""