feat: 客服封存订单功能（号主失联场景）

新增客服「封存订单」动作，用于号主失联、无法联系的场景：单事务内
完成关闭订单、全量原路退款、永久封存关联商品、解散发布群、双方通知
与审计日志。

- 新增 listing 终态 sealed（封存），区别于可恢复的 offline
- listingLockedForOwnerMutation 锁定 sealed，号主无法再编辑/提审/上架
- 解散群聊按 listing_id 查发布群（listing_group）置 archived，
  阻断所有成员发言并留系统消息
- 新增 order.AdminSeal 及 /admin/orders/:id/seal 路由
- 前端：卖家页 PC/移动端 sealed 视为终态禁用操作，客服后台新增
  「封存订单」按钮与二次确认

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/internal/modules/order/constants.go

@@ -50,17 +50,20 @@ const (
 	listingStatusOffline   = "offline"
 	listingStatusCompleted = "completed"
 	listingStatusAbnormal  = "abnormal"
+	listingStatusSealed    = "sealed"
 
 	accountStatusPublished = "published"
 	accountStatusRented    = "rented"
 	accountStatusOffline   = "offline"
 	accountStatusAbnormal  = "abnormal"
+	accountStatusSealed    = "sealed"
 
 	walletBizOwnerIncome         = "owner_income"
 	walletBizDepositCompensation = "deposit_compensation"
 
 	refundBizCancel     = "cancel_refund"
 	refundBizAdminClose = "admin_close_refund"
+	refundBizAdminSeal  = "admin_seal_refund"
 	refundBizAdmin      = "admin_refund"
 	refundBizCheckout   = "checkout_refund"
 )