feat: MQTT 双主题同步到 vd960DBN 固件 + DBNMQTTool devlog

vd960DBN 固件改动:
- net_srv.h: 默认 topic 改为 dld960/{sn}/srv + dld960/{sn}/dev
- net_srv.c: dg_subscribe_display_topic() 直接用 topic_sub 订阅（不再追加 client_id/sn 后缀）
- net_srv.c: mqtt_deserialize_publish() topic 过滤改用 g_iot_topic.topic_sub（不再硬编码 TOPIC_DEFAULT_SUBSCRIBE）

DBNMQTTool 文档:
- devlog.md: 清理过期 topic 引用语义

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/net_srv.c

@@ -137,17 +137,13 @@ void dg_subscribe_display_topic(void)
     }
     memset(mBuff, 0, 256);
     
-    if(g_iot_topic.clientid_enable)
-    {
-        sprintf(mBuff, "%s/%s", g_iot_topic.topic_sub, iot_net_info.client_id);
-    }
-    else
-    {
-        sprintf(mBuff, "%s/%s", g_iot_topic.topic_sub, g_dev_number_str);
-    }
+    // V1.01: 双主题协议 — topic_sub 即为完整订阅主题，不再追加后缀
+    strcpy(mBuff, (char *)g_iot_topic.topic_sub);
     
     {
-    PRINT("\r\nWill subscribe display_topic:\n%s\r\n", mBuff);
+    PRINT("
+\nWill subscribe display_topic:\n%s
+\n", mBuff);
     }
     MQTT_Subscribe(mBuff, 1);
     
@@ -225,9 +221,11 @@ void mqtt_deserialize_publish(char* topic, char* msg, int length)
 {    
 //    if(g_flag_debug)
 //    {
-//        printf("display_mqtt_callback rev topic: %s\n msg:%s, len:%d\r\n", topic, msg, length);
+//        printf("display_mqtt_callback rev topic: %s\n msg:%s, len:%d
+\n", topic, msg, length);
 //    }
-    if(strstr(topic, (char *)TOPIC_DEFAULT_SUBSCRIBE) != NULL)  //
+    // V1.01: 使用配置的 topic_sub 匹配，而非硬编码默认值
+    if(strstr(topic, (char *)g_iot_topic.topic_sub) != NULL)
     {
         manage_mqtt_recv_message(msg, length);
     }