fix(telegram): route gw: gateway-pick taps to on_pick_gateway

The root Dispatcher's own @dp.callback_query(StateFilter(None), ~pax:) catch-all is checked before included sub-routers, so it was swallowing every gw: gateway-selection tap (state is cleared before the menu shows). Exclude gw: from it, mirroring the existing pax: exclusion, so the tap propagates to booking_flow.router.on_pick_gateway.

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com