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.wxml

@@ -20,7 +20,12 @@
 
     <view class="page-title">选择订阅套餐</view>
 
-    <view class="service-card">
+    <view class="loading-plans" wx:if="{{loadingPlans}}">
+      <view class="loading-spinner"></view>
+      <text class="loading-text">加载套餐中...</text>
+    </view>
+
+    <view class="service-card" wx:if="{{!loadingPlans}}">
       <view class="service-icon">✨</view>
       <view class="service-info">
         <view class="service-name">智能模式</view>
@@ -28,7 +33,7 @@
       </view>
     </view>
 
-    <view class="plans">
+    <view class="plans" wx:if="{{!loadingPlans}}">
       <view class="plan {{selected === item.key ? 'selected' : ''}} {{item.disabled ? 'plan-disabled' : ''}}" wx:for="{{plans}}" wx:key="key" bindtap="{{item.disabled ? '' : 'onSelect'}}" data-plan="{{item.key}}">
         <view class="plan-tag {{item.disabled ? 'plan-tag-disabled' : (selected === item.key ? 'plan-tag-active' : '')}}" wx:if="{{item.tag}}">{{item.tag}}</view>
         <view class="plan-price">{{item.priceLabel}}</view>
@@ -37,9 +42,11 @@
       </view>
     </view>
 
-    <button class="btn-primary btn-primary-gold" bindtap="onPurchase" disabled="{{purchasing}}" loading="{{purchasing}}">
-      {{subscription && subscription.status === 'active' && subRemaining > 0 ? '续费' : '确认支付'}}
-    </button>
-    <view class="agreement" bindtap="onAgreement">支付即表示同意《订阅协议》</view>
+    <block wx:if="{{!loadingPlans}}">
+      <button class="btn-primary btn-primary-gold" bindtap="onPurchase" disabled="{{purchasing}}" loading="{{purchasing}}">
+        {{subscription && subscription.status === 'active' && subRemaining > 0 ? '续费' : '确认支付'}}
+      </button>
+      <view class="agreement" bindtap="onAgreement">支付即表示同意《订阅协议》</view>
+    </block>
   </view>
 </view>