Add media gallery with album organization and Puck integration

Backend:
- Add Album and MediaFile models for tenant-scoped media storage
- Add TenantStorageUsage model for per-tenant storage quota tracking
- Create StorageQuotaService with EntitlementService integration
- Add AlbumViewSet, MediaFileViewSet with bulk operations
- Add StorageUsageView for quota monitoring

Frontend:
- Create MediaGalleryPage with album management and file upload
- Add drag-and-drop upload with storage quota validation
- Create ImagePickerField custom Puck field for gallery integration
- Update Image, Testimonial components to use ImagePicker
- Add background image picker to Puck design controls
- Add gallery to sidebar navigation

Also includes:
- Puck marketing components (Hero, SplitContent, etc.)
- Enhanced ContactForm and BusinessHours components
- Platform login page improvements
- Site builder draft/preview enhancements

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/i18n/locales/en.json

@@ -91,6 +91,10 @@
       "subtitle": "Sign in to manage your appointments",
       "staffAccess": "Staff Access",
       "customerBooking": "Customer Booking"
+    },
+    "platformLogin": {
+      "title": "Platform Staff Login",
+      "subtitle": "Authorized personnel only"
     }
   },
   "nav": {