feat(telegram): promo bot + channel-chat moderation gate

Add a second standalone promo bot to the bot container (answers /start with a
localized message + a URL button into the main bot's Mini App) and gate write
access in a channel's linked discussion chat: grant on join when the Telegram
user is registered and neither admin-suspended nor holding a new chat_muted
role, and revoke/grant on the matching moderation change for a member currently
in the chat.

Eligibility (registered AND NOT suspended AND NOT chat_muted; the game
suspension dominates) is resolved once in the backend and reached two ways: the
bot's join-time unary ResolveChatEligibility over the existing mTLS bot-link,
and a backend chat_access_changed event -> gateway -> ChatGate command
(idempotent; a temporary-block-expiry sweeper may over-emit). The bot guards the
block/unblock path with getChatMember, since bots cannot list members.

A web_app button cannot open another bot's Mini App (it signs initData with the
sending bot's token), so the promo button is a t.me ?startapp URL reusing the
UI's VITE_TELEGRAM_LINK. The bot must be a chat admin with the restrict-members
right and chat_member in its allowed updates.

No schema change: chat_muted reuses the data-driven account_roles table.

.gitea/workflows/ci.yaml

@@ -260,11 +260,16 @@ jobs:
           GM_BASICAUTH_HASH: ${{ secrets.TEST_GM_BASICAUTH_HASH }}
           GRAFANA_ADMIN_PASSWORD: ${{ secrets.TEST_GRAFANA_ADMIN_PASSWORD }}
           TELEGRAM_BOT_TOKEN: ${{ secrets.TEST_TELEGRAM_BOT_TOKEN }}
+          TELEGRAM_PROMO_BOT_TOKEN: ${{ secrets.TEST_TELEGRAM_PROMO_BOT_TOKEN }}
           GM_BASICAUTH_USER: ${{ vars.TEST_GM_BASICAUTH_USER }}
           GRAFANA_ROOT_URL: ${{ vars.TEST_GRAFANA_ROOT_URL }}
           CADDY_SITE_ADDRESS: ${{ vars.TEST_CADDY_SITE_ADDRESS }}
           TELEGRAM_MINIAPP_URL: ${{ vars.TEST_TELEGRAM_MINIAPP_URL }}
           TELEGRAM_GAME_CHANNEL_ID: ${{ vars.TEST_TELEGRAM_GAME_CHANNEL_ID }}
+          TELEGRAM_CHAT_ID: ${{ vars.TEST_TELEGRAM_CHAT_ID }}
+          TELEGRAM_BOT_USERNAME: ${{ vars.TEST_TELEGRAM_BOT_USERNAME }}
+          # The promo button reuses the UI's Mini App link variable.
+          TELEGRAM_BOT_LINK: ${{ vars.TEST_VITE_TELEGRAM_LINK }}
           # The test contour always uses Telegram's test environment — pinned here,
           # not an operator variable. The prod workflow leaves it false.
           TELEGRAM_TEST_ENV: "true"