feat(telegram): button-driven menu (flight/hotel/advisor/bookings/language), drop commands
- Replace persistent menu with 5 buttons: پرواز/هتل/مشاور سفر (row 1), رزروها/انتخاب زبان (row 2). Flight/hotel/advisor taps send a bridge-local example message (no core turn); bookings -> tap:bookings:list; language -> picker.
- Remove all slash commands except /start (delete_my_commands); drop the /new_search, /cancel, /my_orders, /human_support, /language handlers and the now-unused _human_support helper + Command/BotCommand imports.
- Reword the 'still missing' passenger prompt to be friendlier in fa/ar/en.
- eval_multiturn: replace the /cancel escape-hatch with a natural-language pivot.
Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com