Add ticket system with QR scanner and PDF generation

- Add ticket validation and check-in API endpoints
- Add PDF ticket generation with QR codes (pdfkit)
- Add admin QR scanner page with camera support
- Add admin site settings page
- Update email templates with PDF ticket download link
- Add checked_in_by_admin_id field for audit tracking
- Update booking success page with ticket download
- Various UI improvements to events and booking pages

frontend/src/app/admin/layout.tsx

@@ -22,6 +22,7 @@ import {
   Bars3Icon,
   XMarkIcon,
   BanknotesIcon,
+  QrCodeIcon,
 } from '@heroicons/react/24/outline';
 import clsx from 'clsx';
 import { useState } from 'react';
@@ -59,12 +60,14 @@ export default function AdminLayout({
     { name: t('admin.nav.dashboard'), href: '/admin', icon: HomeIcon },
     { name: t('admin.nav.events'), href: '/admin/events', icon: CalendarIcon },
     { name: t('admin.nav.bookings'), href: '/admin/bookings', icon: TicketIcon },
+    { name: locale === 'es' ? 'Escáner' : 'Scanner', href: '/admin/scanner', icon: QrCodeIcon },
     { name: t('admin.nav.users'), href: '/admin/users', icon: UsersIcon },
     { name: t('admin.nav.payments'), href: '/admin/payments', icon: CreditCardIcon },
     { name: locale === 'es' ? 'Opciones de Pago' : 'Payment Options', href: '/admin/payment-options', icon: BanknotesIcon },
     { name: t('admin.nav.contacts'), href: '/admin/contacts', icon: EnvelopeIcon },
     { name: t('admin.nav.emails'), href: '/admin/emails', icon: InboxIcon },
     { name: t('admin.nav.gallery'), href: '/admin/gallery', icon: PhotoIcon },
+    { name: locale === 'es' ? 'Configuración' : 'Settings', href: '/admin/settings', icon: Cog6ToothIcon },
   ];
 
   const handleLogout = () => {