feat: MQTT 协议 V1.01 — Topic 压缩为双主题 (up/down)

- 7个主题压缩为2个: dld960/{sn}/down + dld960/{sn}/up
- 消息类型由 JSON cmd 字段区分，不再依赖 topic 路径
- protocol.py: topic_up()/topic_down() 替代旧7个函数
- mqtt_client.py: 4个通配符订阅→1个 dld960/+/up
- main.py: 消息路由改为 cmd 匹配，协议Topic树简化
- 文档更新 V1.01

DBNMQTTool/dbn_mqtt_tool/mqtt_client.py

@@ -68,14 +68,8 @@ class MqttClient:
             self._connected = True
             self._notify_status(True, "已连接到 Broker")
 
-            from .protocol import (
-                TOPIC_ALL_CONFIG_RESP, TOPIC_ALL_DATA_LOOP,
-                TOPIC_ALL_DATA_EVENT, TOPIC_ALL_STATUS
-            )
-            client.subscribe(TOPIC_ALL_CONFIG_RESP, qos=1)
-            client.subscribe(TOPIC_ALL_DATA_LOOP, qos=1)
-            client.subscribe(TOPIC_ALL_DATA_EVENT, qos=1)
-            client.subscribe(TOPIC_ALL_STATUS, qos=0)
+            from .protocol import TOPIC_ALL_DEVICE_UP
+            client.subscribe(TOPIC_ALL_DEVICE_UP, qos=1)
         else:
             self._connected = False
             self._notify_status(False, f"连接失败 (rc={rc})")