Thread the Telegram bot's service language (en/ru) from the session mint response
through the gateway into the FlatBuffers Session, so the UI knows which bot the
player signed in through. handleTelegramAuth refreshes the account's service
language onto the response before minting (it was set after the fetched copy).
Empty for a non-Telegram login.
Service-agnostic refinement of the owner's idea: the sign-in service returns a
set of supported game languages with the user identity, and the lobby gates the
New Game variant choice by it (en -> English; ru -> Russian + Эрудит).
- Connector hosts two bots in one container (one per service language, each its
own token + game channel; the same telegram_id spans both). ValidateInitData
tries each token and returns the validating bot's service_language +
supported_languages. Per-language config (TELEGRAM_BOT_TOKEN_EN/_RU, channels).
- supported_languages rides the Session (fbs, session-scoped, not persisted); the
UI offers only the matching variants on New Game — gating only the START of a
new game (auto-match + friend invite), not accept/open/play; backend does not
enforce.
- service_language persisted (accounts.service_language, migration 00010, written
every login, last-login-wins) and routes the user-facing Notify push back
through the right bot (push-target coalesces with preferred_language).
- Admin SendToUser/SendToGameChannel gain an operator-chosen language selector in
the console (unrelated to ValidateInitData).
- Non-Telegram logins carry the gateway default set
(GATEWAY_DEFAULT_SUPPORTED_LANGUAGES, all variants).
Wire (committed regen): ValidateInitDataResponse +service_language
+supported_languages; Session +supported_languages; SendToUser/SendToGameChannel
+language. Docs (ARCHITECTURE/FUNCTIONAL/_ru/READMEs) + PLAN updated; stage marked done.