[AI Generated]: refactor(*): 保活定时器与连接清理逻辑收口至 app.js，修复 null 安全与注释错误

- 新增 app.startKeepAlive/stopKeepAlive/cleanupConnection，bus 监听自动控制保活与断联清理
- Blue.stop() 收入 cleanupConnection，页面 onHide/onUnload 统一调用
- 修复 replaceNetwork.js seviceList 可能为 undefined 导致崩溃
- 修复 configureDevice_2.js device.mac 为 null 时崩溃
- 修复 replaceNetwork_1.js activeProtocol 无 null 检查及 wifiList 容错
- 修正 configureDevice_4.js 超时注释（3分钟→30秒）

pages/replaceNetwork/replaceNetwork.js

@@ -59,7 +59,6 @@ Page({
                     const nameArr = this.data.device.name.split("-");
                     app.globalData.ppScale.version = nameArr.length === 5 ? "domain2" : "domain1";
                     wx.hideLoading();
-                    this._startKeepAlive();
                     if (this.data.progress === 0) {
                         const comp = this.selectComponent('#replaceNetwork1Component');
                         if (comp) comp.getWiFiList();
@@ -193,6 +192,11 @@ Page({
             let seviceList = app.globalData.ppScale.device.setting.find((item) => {
                 return item.deviceName === res.result[0].type
             });
+            if (!seviceList) {
+                wx.hideLoading();
+                wx.showToast({ title: '未找到匹配的设备类型', icon: 'none' });
+                return;
+            }
             app.globalData.ppScale.plugin.Blue.setDeviceSetting([seviceList]);
             app.globalData.ppScale.plugin.Blue.start(res.result[0].type, false);
             app.globalData.ppScale.plugin.bus.subscribe("devicesList", (res_) => {
@@ -262,39 +266,14 @@ Page({
         }
     },
 
-    // 启动保活定时器，每10秒发送一次保活指令
-    _keepAliveTimer: null,
-    _startKeepAlive() {
-        this._stopKeepAlive();
-        this._keepAliveTimer = setInterval(() => {
-            if (app.globalData.ppScale.activeProtocol) {
-                app.globalData.ppScale.activeProtocol.sendKeepAliveCode();
-            }
-        }, 15000);
-    },
-
-    // 清除保活定时器
-    _stopKeepAlive() {
-        if (this._keepAliveTimer) {
-            clearInterval(this._keepAliveTimer);
-            this._keepAliveTimer = null;
-        }
-    },
-
     onHide() {
         console.log("replaceNetwork onHide");
-        this._stopKeepAlive();
-        app.resetReconnectCount();
-        app.setGlobalData('ppScale.device.connectState', null);
-        app.globalData.ppScale.plugin.Blue.stop();
+        app.cleanupConnection();
     },
 
     onUnload() {
         console.log("replaceNetwork onUnload");
-        this._stopKeepAlive();
-        app.resetReconnectCount();
-        app.setGlobalData('ppScale.device.connectState', null);
-        app.globalData.ppScale.plugin.Blue.stop();
+        app.cleanupConnection();
         if (this._connectStateWatcher) {
             app.unwatch('ppScale.device.connectState', this._connectStateWatcher);
         }