feat(ui): real friend-invite share with a per-bot link

The friend-code 'share' was an <a> that just opened the bot. Make it a real share:
Telegram's native share-to-chat picker inside the Mini App (openTelegramLink +
t.me/share/url), the system share sheet (navigator.share) on the web, else copy the
link. The shared deep link points at the same bot the player is in — it picks
VITE_TELEGRAM_LINK_EN/_RU by the session's service language, falling back to the
single VITE_TELEGRAM_LINK. Adds the per-bot build args across Dockerfile / compose /
ci.yaml / .env / docs; PLAN TODO-5 updated.

ui/README.md

@@ -28,8 +28,11 @@ 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. `VITE_TELEGRAM_BOT_ID`
 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. `VITE_TELEGRAM_GAME_CHANNEL_NAME_EN` / `VITE_TELEGRAM_GAME_CHANNEL_NAME_RU`
+domain is registered with BotFather (`/setdomain`); `VITE_TELEGRAM_LINK_EN` /
+`VITE_TELEGRAM_LINK_RU` are the per-bot friend-invite Mini App links (full URL
+`https://t.me/<bot>/<app>`; the share picks the one matching the bot the player
+signed in through, falling back to `VITE_TELEGRAM_LINK`).
+`VITE_TELEGRAM_GAME_CHANNEL_NAME_EN` / `VITE_TELEGRAM_GAME_CHANNEL_NAME_RU`
 are the per-language "Play in Telegram" links shown on the landing page.
 
 The build has **two entries**: the game SPA (`index.html`, served at `/app/` and