feat: blacklist, guest lookup, bank transfer payment page

- Add is_blacklisted column to guests (migration 068)
- POST /widget/bookings: block blacklisted guests (403, generic message)
- GET /widget/:slug/guests/lookup: find existing guest by email/phone for auto-fill
- Widget form: debounce guest lookup on email/phone input, show "Заполнить" suggestion
- Widget payment screen: replace fake card form with proper YooKassa redirect screen or bank transfer details page
- Add bank transfer details field to widget settings (saved as widget_bank_details)
- GuestsPage: blacklist toggle button in edit modal + 🚫 ЧС badge in table

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

src/pages/BookingWidgetStandalonePage.tsx

@@ -23,6 +23,7 @@ export function BookingWidgetStandalonePage() {
     showPromo:       searchParams.get('promo') !== 'false',
     allowExtraBeds:  searchParams.get('extra-beds') !== 'false',
     allowChildren:   searchParams.get('children') !== 'false',
+    bankDetails:     '',
     formFields:      DEFAULT_FORM_FIELDS,
     additionalServices: DEFAULT_SERVICES,
   })
@@ -47,6 +48,7 @@ export function BookingWidgetStandalonePage() {
             showPromo:       ws.showPromo        ?? prev.showPromo,
             allowExtraBeds:  ws.allowExtraBeds   ?? prev.allowExtraBeds,
             allowChildren:   ws.allowChildren    ?? prev.allowChildren,
+            bankDetails:     ws.bankDetails      ?? prev.bankDetails,
           }))
         } else {
           setSettings(prev => ({ ...prev, hotelName: config.hotelName ?? prev.hotelName }))