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/src/lib/i18n/en.ts

@@ -234,6 +234,8 @@ export const en = {
   'friends.copy': 'Copy',
   'friends.codeCopied': 'Code copied.',
   'friends.shareTelegram': 'Share via Telegram',
+  'friends.inviteText': "Let's be friends in Scrabble!",
+  'friends.linkCopied': 'Link copied.',
   'friends.added': 'Added {name}.',
   'friends.blockedList': 'Blocked players',
   'friends.unblock': 'Unblock',