feat: complete feature gaps across all modules

Server:
- Add settings-cache with 60s TTL for feature toggle checks
- Enforce maintenance_mode on login, enable_binding on device bind

Admin console:
- Remove dead "发送通知" button from user detail
- Firmware check calls real API and compares versions

Miniprogram:
- Wear-check: dynamic battery/connected from BLE state
- Login: hide non-functional phone auth button
- Treating: show actual selected regions instead of hardcoded "全脸"
- Index: display subscription status with tap to manage
- Auto-scan: show "待检测" instead of "--" for PD data
- Agreements: tap shows "内容建设中" modal

miniprogram/pages/wear-check/wear-check.js

@@ -7,7 +7,9 @@ Page({
     checking: false,
     result: null,
     error: '',
-    devMode: false
+    devMode: false,
+    battery: 0,
+    connected: false
   },
 
   onBack: function () {
@@ -21,6 +23,11 @@ Page({
   onLoad: function () {
     var app = getApp()
     this.setData({ statusBarHeight: app.globalData.statusBarHeight, devMode: config.__DEV__ || false })
+    var device = app.globalData.currentDevice || {}
+    this.setData({
+      battery: device.battery || 0,
+      connected: ble.isConnected()
+    })
   },
 
   onShow: function () {
@@ -34,6 +41,9 @@ Page({
     if (this._onStatus) ble.off('status', this._onStatus)
     this._onStatus = function (status) {
       self.setData({ checking: false })
+      if (status.battery !== undefined) {
+        self.setData({ battery: status.battery, connected: true })
+      }
       if (status.bind_status === 1) {
         self.setData({ result: 'ok' })
       } else {

miniprogram/pages/wear-check/wear-check.wxml

@@ -11,9 +11,10 @@
       <view class="device-row-info">
         <view class="device-row-name">
           光子美容仪
-          <text class="status-badge status-badge-green">已连接</text>
+          <text class="status-badge status-badge-green" wx:if="{{connected}}">已连接</text>
+          <text class="status-badge" style="background:#ccc;" wx:else>未连接</text>
         </view>
-        <view class="device-row-battery">电量 85%</view>
+        <view class="device-row-battery">电量 {{battery}}%</view>
       </view>
     </view>