feat(ui): refine Telegram invite & close UX

- Shared invite links open the Mini App fullscreen (mode=fullscreen), so a
  shared link matches the bot's own fullscreen launch.
- A used or expired invite deep-link now lands the visitor in the lobby with a
  gentle notice pointing at the right bot (@<username>, by service language),
  instead of a red "code invalid/expired" error on the Friends screen.
- The in-game close confirmation is armed only on Telegram mobile clients; on
  desktop (tdesktop/macOS/web) it is skipped, where the "changes may not be
  saved" dialog is just noise (drafts auto-save).

ui/src/lib/i18n/en.ts

@@ -237,6 +237,8 @@ export const en = {
   'friends.inviteText': "Let's play Scrabble!",
   'friends.linkCopied': 'Link copied.',
   'friends.selfInvite': "Hopefully you've been friends with yourself for a while ☺️",
+  'friends.staleInviteTitle': 'Link expired',
+  'friends.staleInvite': 'You opened the game from an outdated link. Open the bot {bot} to play and get notifications.',
   'friends.added': 'Added {name}.',
   'friends.blockedList': 'Blocked players',
   'friends.unblock': 'Unblock',