fix: resolve 8 bugs and add admin features

Miniprogram:
- Profile "我的设备": show unbind option when device bound, scan when not
- Add device status indicator (已绑定/未绑定) to profile menu

Admin console:
- Login: add @confirm to inputs so Enter key submits the form
- Record detail: wire up 详情 link with modal showing full record info
- Dashboard: add subscription stats row (月卡/年卡/试用/收入)
- Subscription: add 取消 action for active subscriptions
- Format: fix -8h timezone display for UTC ISO date strings

Server:
- POST /api/v1/admin/subscriptions/cancel: cancel active subscriptions
- Dashboard API: include sub_stats (plan counts + monthly revenue)
- IP extraction: add X-Forwarded-For fallback for logging

miniprogram/pages/profile/profile.wxml

@@ -20,6 +20,8 @@
       <view class="menu-item" bindtap="onManageDevice">
         <view class="menu-icon">📱</view>
         <view class="menu-text">我的设备</view>
+        <text class="menu-device-status" wx:if="{{deviceCount > 0}}">已绑定</text>
+        <text class="menu-device-status menu-device-unbound" wx:else>未绑定</text>
         <text class="menu-arrow">›</text>
       </view>
       <view class="menu-item" bindtap="onViewHistory">