feat(bookings): add payment and document upload to confirmation page

Allow users to select payment method and upload receipts before confirming.
Add public API endpoints for payment updates and document management.

server/utils/bookings.ts

@@ -106,6 +106,20 @@ export function parseBookingPicTransferInput(body: {
   }
 }
 
+export function parsePaymentMethodInput(body: {
+  paymentMethod?: PaymentMethod | string | null
+}) {
+  const paymentMethod = typeof body.paymentMethod === 'string'
+    ? body.paymentMethod.trim().toLowerCase()
+    : body.paymentMethod
+
+  assertBadRequest(isPaymentMethod(paymentMethod), 'Payment method must be Cash or Bank')
+
+  return {
+    paymentMethod
+  }
+}
+
 export function buildBookingMessage(booking: PublicBooking, confirmationUrl: string) {
   if (booking.locale === 'zh') {
     return [