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/en.json

@@ -442,7 +442,9 @@
     "PROVIDER_NOT_LINKED": "The provider hasn’t opened the work bot via the invite yet — nowhere to send messages.",
     "CARD_EXPIRED": "The QR is out of date or invalid — ask the client to reopen the card.",
     "OFFER_NOT_AVAILABLE": "This offer isn’t available at the client’s level.",
-    "OFFER_LIMIT_REACHED": "The limit for this offer is already used up."
+    "OFFER_LIMIT_REACHED": "The limit for this offer is already used up.",
+    "CONCIERGE_SUBSCRIBERS_ONLY": "The personal concierge is for Barev+ and Barev Elite members. For now, write to support — we will help too.",
+    "ASSIGNEE_NO_ACCESS": "This team member has no access to this channel."
   },
   "client": {
     "nav": {
@@ -654,6 +656,20 @@
       "used_ONCE": "already used",
       "used_WEEK": "again next week",
       "used_MONTH": "again next month"
+    },
+    "chat": {
+      "title": "Chat with Barev Club",
+      "support": "Support",
+      "concierge": "Personal concierge",
+      "hint": "This is the same conversation as in the bot chat: replies arrive here and in Telegram.",
+      "empty": "Tell us how we can help — we’ll reply here.",
+      "placeholder": "Message…",
+      "send": "Send",
+      "attach": "Attach a photo or file",
+      "conciergeOnly": "The personal concierge comes with Barev+ and Barev Elite",
+      "team": "Barev Club",
+      "fileTooBig": "The file is larger than 10 MB",
+      "file": "File"
     }
   },
   "pro": {
@@ -815,7 +831,12 @@
       "cmdHelp": "Help",
       "webRequestOrdered": "Request No. {{request}} received and booked as order No. {{order}} for {{date}}. Track the status in the app.",
       "webRequestLinked": "Request No. {{request}} received. An operator will contact you to confirm the time.",
-      "conciergeReceived": "Passed to the concierge — we'll reply here, in this chat."
+      "conciergeReceived": "Passed to the concierge — we'll reply here, in this chat.",
+      "supportReceived": "Passed to support — we'll reply here, in this chat.",
+      "channelSupport": "You are now writing to support. Just send a message, photo or file.",
+      "channelConcierge": "You are now writing to your personal concierge. Just send a message, photo or file.",
+      "cmdSupport": "Write to support",
+      "cmdConcierge": "Write to the concierge (Barev+)"
     },
     "pro": {
       "notLinked": "This bot is for Barev Club specialists. Ask the operator for an invite link.",
@@ -844,7 +865,11 @@
       "newRequest": "App request #{{number}}",
       "newWebRequest": "Site request #{{number}}",
       "loginOk": "Sign-in confirmed — go back to your browser.",
-      "loginExpired": "The sign-in link has expired — reload the admin page."
+      "loginExpired": "The sign-in link has expired — reload the admin page.",
+      "channelSupport": "Support",
+      "channelConcierge": "Concierge",
+      "file": "file",
+      "chatAssigned": "{{by}} passed you a conversation: {{name}}"
     },
     "partner": {
       "valid": "{{name}} — {{level}}, card is valid",
@@ -948,7 +973,8 @@
     "openPlan": "Open the app",
     "concierge": "Barev Club concierge",
     "subscriptionActivated": "{{plan}} is on until {{date}}. Discounts are already in service prices.",
-    "operator": "Barev Club operator"
+    "operator": "Barev Club operator",
+    "support": "Barev Club support"
   },
   "admin": {
     "nav": {