fix: 放弃 close+recreate listen socket, 改为只关数据socket

根因: WCHNET ERR_ISCONN(0x1D), listen socket 关闭后端口5960仍被占用,
      无法在同端口立即重建. WCHNET_MainTask 循环也未能释放.

新方案: tcp_json_restart 只关数据 socket(N+1) 断开客户端,
        listen socket(N) 保持不动, 仅重置应用层状态.
        新客户端连接时 CONNECT 事件照常触发.

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/tcp_json_srv.c

@@ -794,39 +794,25 @@ static void json_sensor_callback(const uint8_t *pkg, uint16_t len)
  *===========================================================================*/
 
 void tcp_json_restart(void) {
-    PRINT("JSON: === auto-restart (count=%d) ===\n", g_json_restart_count);
+    PRINT("JSON: === restart (count=%d) ===\n", g_json_restart_count);
 
-    /* 1. 关闭数据 socket 和监听 socket */
+    /*
+     * WCHNET 限制: listen socket 关闭后无法在同端口立即重建 (ERR_ISCONN).
+     * 因此只关数据 socket 断开客户端, listen socket 保持不变.
+     */
     if (g_json_socket_listen != 0xFF) {
         WCHNET_SocketClose(g_json_socket_listen + 1, TCP_CLOSE_NORMAL);
-        WCHNET_SocketClose(g_json_socket_listen, TCP_CLOSE_NORMAL);
-        g_json_socket_listen = 0xFF;
     }
 
-    /* 1.5 WCHNET 资源回收 — SocketClose 是异步的, 需跑一轮 MainTask */
-    {
-        uint8_t _retry;
-        for (_retry = 0; _retry < 5; _retry++) {
-            WCHNET_MainTask();
-            if (WCHNET_QueryGlobalInt()) {
-                WCHNET_HandleGlobalInt();
-            }
-            Delay_Ms(10);
-        }
-    }
-
-    /* 2. 重置状态 */
+    /* 重置应用层状态 — listen socket 继续监听 */
     g_json_auth_state  = JSON_STATE_WAIT_AUTH;
     g_json_pwd_retry   = 0;
     g_json_recv_len    = 0;
     g_json_last_comm_ts    = 0;
     g_json_last_connect_ts = 0;
-    g_json_auth_timer  = 0;
+    g_json_auth_timer  = mstick();       // 从此刻重新计时
     g_json_lockout_timer  = 0;
     g_json_pending.active = 0;
-
-    /* 3. 重新创建 socket 并监听 */
-    tcp_json_srv_init();
 }
 
 #define TCP_JSON_SRV_INIT_MAX_RETRY 3