fix: booking widget payment flow and success message

- On API error: show error message instead of false success screen
- Success message: "Оплата прошла успешно" only when paidViaGateway=true (user actually clicked pay in YooKassa); otherwise "Бронирование принято. Менеджер свяжется с вами" or "Оплата на месте"
- Payment screen: simplified to YooKassa-only redirect (removed bank transfer variant)
- Removed bankDetails from WidgetSettings entirely (not needed per product decision)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/api.ts

@@ -1680,7 +1680,6 @@ export interface WidgetConfig {
     allowExtraBeds: boolean
     allowChildren: boolean
     hotelName: string
-    bankDetails: string
   }
 }