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/(public)/booking/success/[ticketId]/page.tsx

@@ -13,6 +13,7 @@ import {
   XCircleIcon,
   TicketIcon,
   ArrowPathIcon,
+  ArrowDownTrayIcon,
 } from '@heroicons/react/24/outline';
 
 export default function BookingSuccessPage() {
@@ -224,6 +225,20 @@ export default function BookingSuccessPage() {
             </p>
           )}
           
+          {/* Download Ticket Button */}
+          {isPaid && (
+            <div className="mb-6">
+              <a 
+                href={`/api/tickets/${ticketId}/pdf`}
+                download
+                className="inline-flex items-center gap-2 px-4 py-2 bg-primary-yellow text-primary-dark font-medium rounded-btn hover:bg-primary-yellow/90 transition-colors"
+              >
+                <ArrowDownTrayIcon className="w-5 h-5" />
+                {locale === 'es' ? 'Descargar Ticket' : 'Download Ticket'}
+              </a>
+            </div>
+          )}
+          
           {/* Actions */}
           <div className="flex flex-col sm:flex-row gap-3 justify-center">
             <Link href="/events">