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.wxss

@@ -98,6 +98,15 @@
   font-size: 32rpx;
 }
 
+.menu-device-status {
+  font-size: 24rpx;
+  color: #52c41a;
+  margin-right: 8rpx;
+}
+.menu-device-unbound {
+  color: #999;
+}
+
 .logout-btn {
   text-align: center;
   color: #ff4d4f;