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)/book/[eventId]/page.tsx

@@ -913,10 +913,12 @@ export default function BookingPage() {
               <MapPinIcon className="w-5 h-5 text-primary-yellow" />
               <span>{event.location}</span>
             </div>
-            <div className="flex items-center gap-3">
-              <UserGroupIcon className="w-5 h-5 text-primary-yellow" />
-              <span>{event.availableSeats} {t('events.details.spotsLeft')}</span>
-            </div>
+            {!event.externalBookingEnabled && (
+              <div className="flex items-center gap-3">
+                <UserGroupIcon className="w-5 h-5 text-primary-yellow" />
+                <span>{event.availableSeats} {t('events.details.spotsLeft')}</span>
+              </div>
+            )}
             <div className="flex items-center gap-3">
               <CurrencyDollarIcon className="w-5 h-5 text-primary-yellow" />
               <span className="font-bold text-lg">