feat: production readiness — feature gaps + config hardening

Miniprogram:
- Add BLE reconnect button on home page when disconnected
- Add loading states to index, profile, subscribe-plans pages
- Add profile editing (avatar + nickname) with COS upload
- Enable pull-to-refresh on history page
- Fix auto-scan self.options → self.data inconsistency
- Add console.error to silent catch blocks
- Gate 'Simple Peripheral' BLE scan behind __DEV__ flag
- Add production config comment to env.js

Admin console:
- Add empty state '暂无数据' to all 5 list views
- Replace plain text plan input with select dropdown
- Add type="date" to record date filters
- Add production config comment

Server:
- CORS origin restricted in production (env CORS_ORIGIN)
- DB pool size configurable via DB_POOL_SIZE env var
- .env.example updated with WeChat Pay + production fields

miniprogram/pages/subscribe-plans/subscribe-plans.js

@@ -8,7 +8,8 @@ Page({
     selected: 'yearly',
     purchasing: false,
     subscription: null,
-    subRemaining: 0
+    subRemaining: 0,
+    loadingPlans: true
   },
 
   onBack: function () {
@@ -31,6 +32,7 @@ Page({
 
   loadPlans: function () {
     var self = this
+    self.setData({ loadingPlans: true })
     api.getPlans().then(function (data) {
       var serverPlans = data.plans || []
       var monthlyPrice = 99
@@ -54,9 +56,11 @@ Page({
         }
       })
       if (plans.length > 0) self.setData({ plans: plans })
+      self.setData({ loadingPlans: false })
       self.checkTrialUsed()
     }).catch(function () {
       self.setData({
+        loadingPlans: false,
         plans: [
           { key: 'trial', name: '试用', price: 0, priceLabel: '免费', desc: '7天免费体验', disabled: false },
           { key: 'monthly', name: '月卡', price: 99, priceLabel: '¥99', desc: '约3.3元/天' },