Stage 15: dual Telegram bots & language-gated variants

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.

platform/telegram/deploy/docker-compose.yml

@@ -44,14 +44,18 @@ services:
       - vpn
     network_mode: "service:vpn"
     environment:
-      # The bot token lives ONLY in this container (ARCHITECTURE.md §12).
-      TELEGRAM_BOT_TOKEN: ${TELEGRAM_BOT_TOKEN:?set TELEGRAM_BOT_TOKEN}
+      # The bot tokens live ONLY in this container (ARCHITECTURE.md §12). One bot per
+      # service language (en/ru); at least one token is required (the connector
+      # validates this at boot — compose cannot express "one of").
+      TELEGRAM_BOT_TOKEN_EN: ${TELEGRAM_BOT_TOKEN_EN:-}
+      TELEGRAM_BOT_TOKEN_RU: ${TELEGRAM_BOT_TOKEN_RU:-}
+      TELEGRAM_GAME_CHANNEL_ID_EN: ${TELEGRAM_GAME_CHANNEL_ID_EN:-}
+      TELEGRAM_GAME_CHANNEL_ID_RU: ${TELEGRAM_GAME_CHANNEL_ID_RU:-}
       TELEGRAM_MINIAPP_URL: ${TELEGRAM_MINIAPP_URL:?set TELEGRAM_MINIAPP_URL}
       TELEGRAM_GRPC_ADDR: ${TELEGRAM_GRPC_ADDR:-:9091}
       # Set to true when deploying into Telegram's test environment.
       TELEGRAM_TEST_ENV: ${TELEGRAM_TEST_ENV:-false}
       TELEGRAM_API_BASE_URL: ${TELEGRAM_API_BASE_URL:-}
-      TELEGRAM_GAME_CHANNEL_ID: ${TELEGRAM_GAME_CHANNEL_ID:-}
 
 networks:
   edge: