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/linktree/page.tsx

@@ -57,7 +57,7 @@ export default function LinktreePage() {
     : null;
 
   return (
-    <div className="min-h-screen bg-gradient-to-b from-primary-dark via-gray-900 to-primary-dark">
+    <div className="min-h-screen" style={{ background: 'linear-gradient(to bottom, #002F44, #001a28, #002F44)' }}>
       <div className="max-w-md mx-auto px-4 py-8 pb-16">
         {/* Profile Header */}
         <div className="text-center mb-8">
@@ -102,9 +102,11 @@ export default function LinktreePage() {
                       ? t('events.details.free')
                       : `${nextEvent.price.toLocaleString()} ${nextEvent.currency}`}
                   </span>
-                  <span className="text-sm text-gray-400">
-                    {nextEvent.availableSeats} {t('events.details.spotsLeft')}
-                  </span>
+                  {!nextEvent.externalBookingEnabled && (
+                    <span className="text-sm text-gray-400">
+                      {nextEvent.availableSeats} {t('events.details.spotsLeft')}
+                    </span>
+                  )}
                 </div>
 
                 <div className="mt-4 bg-primary-yellow text-primary-dark font-semibold py-3 px-4 rounded-xl text-center transition-all duration-200 group-hover:bg-yellow-400">