feat(lefu): 切后台挂起连接、回前台自动重连

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

miniprogram/app.ts

@@ -1,6 +1,9 @@
- App<IAppOption>({
+ import { leFuService } from './lefu/index'
+
+App<IAppOption>({
     globalData: {
-        operationsEngineer: false
+        operationsEngineer: false,
+        wasConnected: false
     },
 
     onLaunch() {
@@ -15,6 +18,23 @@
         }
     },
 
+    onHide() {
+        // 切后台：记录连接状态，挂起（断开但保留缓存设备，回前台可重连）
+        const wasConnected = leFuService.isConnected
+        this.globalData.wasConnected = wasConnected
+        if (wasConnected) {
+            leFuService.suspend()
+        }
+    },
+
+    onShow() {
+        // 回前台：如果之前连接过，自动重连
+        if (this.globalData.wasConnected) {
+            this.globalData.wasConnected = false
+            leFuService.autoConnect()
+        }
+    },
+
     getWxLoginCode(): Promise<string> {
         return new Promise((resolve, reject) => {
             wx.login({