Add per-quantity TPago payment links for multi-ticket checkout.

Each ticket quantity (1-5) can have its own TPago link so checkout, emails, and admin config use the correct fixed-amount URL.

frontend/src/app/(public)/booking/[ticketId]/page.tsx

@@ -5,7 +5,7 @@ import { useParams, useSearchParams } from 'next/navigation';
 import Link from 'next/link';
 import { useLanguage } from '@/context/LanguageContext';
 import { ticketsApi, paymentOptionsApi, Ticket, PaymentOptionsConfig } from '@/lib/api';
-import { formatPrice, formatDateLong, formatTime } from '@/lib/utils';
+import { formatPrice, formatDateLong, formatTime, getTpagoLink } from '@/lib/utils';
 import Card from '@/components/ui/Card';
 import Button from '@/components/ui/Button';
 import { 
@@ -305,6 +305,7 @@ export default function BookingPaymentPage() {
   if (step === 'manual_payment' && ticket && paymentConfig) {
     const isBankTransfer = ticket.payment?.provider === 'bank_transfer';
     const isTpago = ticket.payment?.provider === 'tpago';
+    const tpagoLink = getTpagoLink(paymentConfig, ticket.bookingTicketCount || 1);
     
     return (
       <div className="section-padding">
@@ -418,9 +419,9 @@ export default function BookingPaymentPage() {
                 <h3 className="font-semibold text-gray-900">
                   {locale === 'es' ? 'Pago con Tarjeta' : 'Card Payment'}
                 </h3>
-                {paymentConfig.tpagoLink && (
+                {tpagoLink && (
                   <a
-                    href={paymentConfig.tpagoLink}
+                    href={tpagoLink}
                     target="_blank"
                     rel="noopener noreferrer"
                     className="flex items-center justify-center gap-2 w-full px-6 py-4 bg-blue-600 text-white rounded-btn hover:bg-blue-700 transition-colors font-medium"