fix: resolve quality audit issues

- utils.js: force UTC+8 output to match MySQL timezone on SCF
- admin subscriptions: return stats (plan counts + revenue) in response
- admin devices: implement keyword search filter
- device-detail: fix binding history field names (bind_time/unbind_time/bind_status)
- user-detail: fix treatment time field (start_time not started_at)
- dashboard: show actual mode per treatment, use sub_stats from dashboard API

server/src/lib/utils.js

@@ -3,7 +3,9 @@ function toMysqlDate(value) {
   const d = new Date(value)
   if (Number.isNaN(d.getTime())) return null
   const pad = n => String(n).padStart(2, '0')
-  return d.getFullYear() + '-' + pad(d.getMonth() + 1) + '-' + pad(d.getDate()) + ' ' + pad(d.getHours()) + ':' + pad(d.getMinutes()) + ':' + pad(d.getSeconds())
+  const offset = 8 * 60
+  const local = new Date(d.getTime() + offset * 60 * 1000)
+  return local.getUTCFullYear() + '-' + pad(local.getUTCMonth() + 1) + '-' + pad(local.getUTCDate()) + ' ' + pad(local.getUTCHours()) + ':' + pad(local.getUTCMinutes()) + ':' + pad(local.getUTCSeconds())
 }
 
 function formatDate(date) {