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/package.json

@@ -11,6 +11,7 @@
   "dependencies": {
     "@heroicons/react": "^2.1.4",
     "clsx": "^2.1.1",
+    "html5-qrcode": "^2.3.8",
     "next": "^14.2.4",
     "qrcode.react": "^4.2.0",
     "react": "^18.3.1",