feat(telegram): bot support relay — per-user forum topics

Users who DM the bot anything but /start are relayed into a private
forum supergroup, one topic per user. Operators (the chat's admins)
reply in the topic and the bot copies it back to the user; an info card
opening each topic carries a Block/Unblock toggle and a Clear button.
State is a small JSON file on a new /data volume — the bot host has no
database. Off by default (TELEGRAM_SUPPORT_CHAT_ID=0): the prod bot is
unchanged until the operator sets the chat id and adds the bot as a
forum admin.

- internal/support: concurrency-safe JSON store (topic map, block list,
  relayed message ids) with field-targeted mutators and atomic save
- bot/support.go: relay both ways via copyMessage, short-TTL admin
  cache, callback buttons, per-user topic-create lock, loop guard
  (skip the bot's own posts), reopen a deleted topic on the next message
- config + compose + CI/prod-deploy: TELEGRAM_SUPPORT_CHAT_ID per
  contour + TELEGRAM_SUPPORT_STATE_DIR; bot-state named volume; /data
  pre-owned by UID 65532 so a fresh volume is writable under distroless
- docs: ARCHITECTURE §15 + decision record, FUNCTIONAL (+ru), README

docs/FUNCTIONAL.md

@@ -272,6 +272,15 @@ marked read once the screen shows it and disappears a week later. A badge on the
 unanswered reply. Guests cannot send feedback (the entry is hidden). A player the operator has
 barred from feedback (a role, not a full account block) sees the send control disabled.
 
+### Telegram support chat
+A user can also reach the operators straight from the Telegram bot: anything they send the bot
+other than `/start` — text, a photo, a voice message, a file — is forwarded into the operators'
+private support group, grouped into a per-user thread. The user sees no automatic reply; an
+operator answers from that thread and the bot delivers the answer back as an ordinary bot message,
+so to the user it is a quiet one-to-one conversation. Operators can block a user (the bot then
+silently ignores their messages) or clear a thread's messages. This is independent of the in-app
+Feedback above — it serves people who write to the bot directly rather than through the app.
+
 ### History & statistics
 Finished games are archived in a dictionary-independent form and exportable to
 GCG; the export is offered **only once a game is finished**, and never for an