Backoffice stage 2: chats (support + concierge, files)

- ChatThread per client/provider and channel; messages get files, internal notes,
  source (bot/mini app) and delivery errors; reply templates. Migration moves old
  concierge messages into threads.
- Routing: subscribers write to the concierge, others to support; /support and
  /concierge in the client bot; staff can take, transfer, close and move threads.
- Telegram: photos/documents from clients and providers, replies with the channel
  header, files sent from storage, notifications only to the assignee or the
  channel's staff, "Reply" into a specific thread.
- New admin: /chats with list, conversation, notes, files, templates, client panel;
  "Message" button on the client card; dashboard counts threads awaiting reply.
- Client mini app: in-app chat screen sharing the same conversation.
- Old admin keeps working on the same data (notes hidden there).
- Tests for routing, notes, assign/close/move, lists, recipients; separate test DB
  via TEST_DB_NAME; dev:chats-demo script.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

packages/i18n/locales/zh.json

@@ -442,7 +442,9 @@
     "PROVIDER_NOT_LINKED": "服务人员尚未通过邀请打开工作机器人，暂时无法发送消息。",
     "CARD_EXPIRED": "二维码已过期或无效——请客户重新打开会员卡。",
     "OFFER_NOT_AVAILABLE": "该优惠不适用于客户当前等级。",
-    "OFFER_LIMIT_REACHED": "该优惠次数已用完。"
+    "OFFER_LIMIT_REACHED": "该优惠次数已用完。",
+    "CONCIERGE_SUBSCRIBERS_ONLY": "专属礼宾仅面向 Barev+ 和 Barev Elite 会员。目前请联系客服，我们同样会帮你。",
+    "ASSIGNEE_NO_ACCESS": "该成员无权访问此频道。"
   },
   "client": {
     "nav": {
@@ -654,6 +656,20 @@
       "used_ONCE": "已使用",
       "used_WEEK": "下周可再次使用",
       "used_MONTH": "下月可再次使用"
+    },
+    "chat": {
+      "title": "与 Barev Club 聊天",
+      "support": "客服",
+      "concierge": "专属礼宾",
+      "hint": "这与机器人聊天是同一个对话：回复会同时出现在这里和 Telegram。",
+      "empty": "告诉我们需要什么帮助，我们会在这里回复。",
+      "placeholder": "输入消息…",
+      "send": "发送",
+      "attach": "附加照片或文件",
+      "conciergeOnly": "专属礼宾包含在 Barev+ 和 Barev Elite 中",
+      "team": "Barev Club",
+      "fileTooBig": "文件超过 10 MB",
+      "file": "文件"
     }
   },
   "pro": {
@@ -815,7 +831,12 @@
       "cmdHelp": "帮助",
       "webRequestOrdered": "申请 {{request}} 号已收到，并已生成订单 {{order}} 号，时间：{{date}}。状态请在应用中查看。",
       "webRequestLinked": "申请 {{request}} 号已收到。客服会联系你确认时间。",
-      "conciergeReceived": "已转给礼宾，我们会在这个聊天中回复你。"
+      "conciergeReceived": "已转给礼宾，我们会在这个聊天中回复你。",
+      "supportReceived": "已转给客服，我们会在这个聊天中回复你。",
+      "channelSupport": "现在你在给客服写信。直接发送消息、照片或文件即可。",
+      "channelConcierge": "现在你在给专属礼宾写信。直接发送消息、照片或文件即可。",
+      "cmdSupport": "联系客服",
+      "cmdConcierge": "联系礼宾（Barev+）"
     },
     "pro": {
       "notLinked": "此机器人供 Barev Club 服务人员使用。请向客服索取邀请链接。",
@@ -844,7 +865,11 @@
       "newRequest": "应用申请 #{{number}}",
       "newWebRequest": "网站申请 #{{number}}",
       "loginOk": "登录已确认，请返回浏览器。",
-      "loginExpired": "登录链接已过期，请刷新管理页面。"
+      "loginExpired": "登录链接已过期，请刷新管理页面。",
+      "channelSupport": "客服",
+      "channelConcierge": "礼宾",
+      "file": "文件",
+      "chatAssigned": "{{by}} 将对话转交给你：{{name}}"
     },
     "partner": {
       "valid": "{{name}} — {{level}}，会员卡有效",
@@ -948,7 +973,8 @@
     "openPlan": "打开应用",
     "concierge": "Barev Club 礼宾",
     "subscriptionActivated": "{{plan}} 已开通，有效期至 {{date}}。服务价格已含折扣。",
-    "operator": "Barev Club 客服"
+    "operator": "Barev Club 客服",
+    "support": "Barev Club 客服支持"
   },
   "admin": {
     "nav": {