Stage 11: account linking & merge (email + Telegram Login Widget)

Link an email (confirm-code) or Telegram (web Login Widget) to the current
account; if the identity already has its own account, merge the two into the
one in use (the current account is primary, except a guest initiator whose
durable counterpart wins). The merge runs in one transaction
(internal/accountmerge): stats + hint wallet summed, paid_account ORed,
identities/games/chat/complaints transferred, friends/blocks de-duplicated,
the secondary kept as a merged_into tombstone so a shared finished game's
no-cascade FKs hold; a shared active game blocks the merge.

- migration 00009: accounts.paid_account, merged_into, merged_at (+ jetgen)
- internal/link orchestrator; session.RevokeAllForAccount on merge
- connector ValidateLoginWidget RPC + loginwidget HMAC validator
- edge ops link.email.request/confirm/merge, link.telegram.confirm/merge;
  supersedes the Stage 8 email.bind.* surface (request never reveals 'taken'
  before the code is verified, so a probe cannot enumerate addresses)
- UI Profile link section + irreversible-merge dialog; Telegram web sign-in
- focused regression tests (merge core, guest inversion, active-game refusal,
  finished-shared-game kept), gateway transcode + connector + UI codec/e2e
- docs: PLAN, ARCHITECTURE 3/4/9, FUNCTIONAL(+ru), module READMEs

ui/README.md

@@ -26,7 +26,10 @@ pnpm codegen      # regenerate src/gen from edge.proto + scrabble.fbs (dev-time)
 ```
 
 `GATEWAY_URL` overrides the dev proxy target; `VITE_GATEWAY_URL` sets the runtime
-gateway origin for a packaged (non-proxied) build.
+gateway origin for a packaged (non-proxied) build. `VITE_TELEGRAM_BOT_ID` (Stage 11)
+enables the "Link Telegram" web sign-in (the Login Widget) — inert until the site
+domain is registered with BotFather (`/setdomain`); `VITE_TELEGRAM_LINK` is the
+share-to-Telegram deep-link base (Stage 9).
 
 ## How it talks to the gateway