fix: improve UX and fix admin console display issues

Miniprogram:
- Add back buttons to all custom-nav pages
- Add debug/mock buttons (BLE connect, wear check, treatment)
  controlled by __DEV__ flag (hidden in prod)

Admin console:
- Fix log page using nonexistent fields (operator_type, target_type)
  now correctly reads admin_id/user_id/action/detail from API
- Fix subscription date fields (started_at→start_time, expired_at→expire_time)
- Wire up subscription detail/extend/renew action buttons
- Wire up device detail "查看完整日志" button
- Add "创建订阅" button to subscription toolbar
- Fix subscription status mapping (2=expired, 3=cancelled)

Docs:
- Add detailed architecture docs for server, miniprogram, admin console

miniprogram/pages/auto-scan/auto-scan.js

@@ -1,4 +1,5 @@
 var ble = require('../../services/ble')
+var config = require('../../config/env')
 
 Page({
   data: {
@@ -8,14 +9,24 @@ Page({
     regions: 0x7F,
     regionData: [],
     timeout: false,
-    error: ''
+    error: '',
+    devMode: false
+  },
+
+  onBack: function () {
+    wx.navigateBack({
+      fail: function () {
+        wx.reLaunch({ url: '/pages/index/index' })
+      }
+    })
   },
 
   onLoad: function (options) {
     var app = getApp()
     this.setData({
       statusBarHeight: app.globalData.statusBarHeight,
-      regions: parseInt(options.regions) || 0x7F
+      regions: parseInt(options.regions) || 0x7F,
+      devMode: config.__DEV__ || false
     })
     this.startScan()
   },
@@ -80,5 +91,17 @@ Page({
     }).catch(function (err) {
       wx.showToast({ title: err.error_msg || '启动失败', icon: 'none' })
     })
+  },
+
+  onMockScanDone: function () {
+    var self = this
+    if (self._progressTimer) clearInterval(self._progressTimer)
+    var mask = parseInt(self.options.regions) || 0x7F
+    wx.redirectTo({
+      url: '/pages/treating/treating?regions=' + mask +
+        '&wavelength=2' +
+        '&duration=600000' +
+        '&mode=1'
+    })
   }
 })

miniprogram/pages/auto-scan/auto-scan.wxml

@@ -1,5 +1,6 @@
 <view class="page">
   <view class="page-header page-header-pink" style="padding-top: {{statusBarHeight + 24}}px;">
+    <view class="nav-back" bindtap="onBack">‹ 返回</view>
     <view class="page-header-title">自动扫描</view>
     <view class="page-header-subtitle">正在识别面部...</view>
   </view>
@@ -15,6 +16,11 @@
 
     <view class="scan-hint">请将面罩对准面部</view>
 
+    <view class="debug-actions" wx:if="{{devMode}}">
+      <view class="debug-label">🔧 调试工具</view>
+      <button class="btn-secondary btn-sm" bindtap="onMockScanDone">模拟扫描完成</button>
+    </view>
+
     <view class="scan-progress" wx:if="{{scanning}}">
       正在扫描... <text class="highlight">{{regionData.length || 3}}</text> 个区域
     </view>