Enhance email templates with clickable links, branding, and improved styling

- Add clickable gallery links in all email templates
- Include application logo in email header and footer (custom or PicPeak default)
- Redesign emails with professional styling matching gallery login page
  - Gray background with white content box
  - PicPeak green header with centered logo
  - Clean typography and proper spacing
  - Responsive design for mobile devices
  - Styled call-to-action buttons
  - Footer with branding and copyright
- Update email processor to fetch branding settings dynamically
- Use proper API URLs for logo images in emails

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

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

frontend/src/components/admin/index.ts

@@ -15,4 +15,8 @@ export { AdminPhotoGrid } from './AdminPhotoGrid';
 export { AdminPhotoViewer } from './AdminPhotoViewer';
 export { PhotoFilters } from './PhotoFilters';
 export { PasswordResetModal } from './PasswordResetModal';
-export { AdminAuthenticatedImage } from './AdminAuthenticatedImage';
+export { AdminAuthenticatedImage } from './AdminAuthenticatedImage';
+export { ThemeCustomizerEnhanced } from './ThemeCustomizerEnhanced';
+export { ThemeDisplay } from './ThemeDisplay';
+export { ThemeEditorModal } from './ThemeEditorModal';
+export { HeroPhotoSelector } from './HeroPhotoSelector';