Add configurable hero logo settings for individual events:
- Logo visibility toggle (show/hide in hero section)
- Logo size options (small, medium, large, xlarge)
- Logo position options (top, center, bottom)
Changes include:
- Database migration for hero_logo_visible, hero_logo_size, hero_logo_position fields
- Backend routes updated to handle new settings
- Frontend admin page with logo customization controls
- HeroGalleryLayout component with dynamic logo rendering
- i18n translations for EN and DE
Also updates .gitignore to exclude test files and artifacts.