feat: long-stay deposit charge + refunds + auto-confirm widget + white page fix

- Widget white page fix: fallback photo when real rooms have no photos array
- Long-stay deposits: if booking > threshold days and toggle on → full charge instead of hold (bypasses YooKassa 7-day limit)
- DepositSettingsPage: toggle + day threshold input for long-stay full payment
- Refund endpoint: POST /deposit/refund supports full and partial refunds via YooKassa refunds API
- DepositWidget: refund UI for yookassa_charge deposits (full/partial, shows remaining amount)
- partially_refunded status support with badge and "Вернуть ещё" button
- Auto-confirm: webhook now auto-confirms booking status on payment.succeeded for widget bookings
- PaymentSettingsPage: auto-confirm toggle per gateway (shown when booking-widget module active)
- Migration 067: long_stay columns on hotel_deposit_settings, auto_confirm_on_payment on gateways, refunded_amount on deposits

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

backend/migrations/067_long_stay_refund.sql

@@ -0,0 +1,12 @@
+-- Long-stay: charge full deposit amount instead of hold (bypass 7-day YooKassa limit)
+ALTER TABLE hotel_deposit_settings
+  ADD COLUMN IF NOT EXISTS long_stay_full_payment BOOLEAN NOT NULL DEFAULT false,
+  ADD COLUMN IF NOT EXISTS long_stay_threshold_days INT NOT NULL DEFAULT 7;
+
+-- Auto-confirm booking on successful online payment (per payment gateway)
+ALTER TABLE hotel_payment_gateways
+  ADD COLUMN IF NOT EXISTS auto_confirm_on_payment BOOLEAN NOT NULL DEFAULT true;
+
+-- Track refunded amount for captured (charged) deposits
+ALTER TABLE booking_deposits
+  ADD COLUMN IF NOT EXISTS refunded_amount NUMERIC(12,2);