Gallery UI overhaul:
- GalleryGrid: replace equal-size grid with CSS columns masonry layout (6 columns),
pure image cards without text/date info, hover gray ring highlight,
favorited items show red heart badge
- GalleryDetail: left-right layout dialog (70% image / 30% info),
nearly full-screen size with minimal margins, black background for image area,
absolute-positioned image container for correct sizing across all aspect ratios,
favorite toggle button replaces tag manager, removed outer border
- Gallery page: added "favorites only" filter button, replaced load-more button
with IntersectionObserver infinite scroll, removed tag system references
Favorites system:
- db.ts: added `favorited` column to media_generations with migration
- New API: PUT /api/media/[id]/favorite for toggle
- gallery/route.ts: support favoritesOnly=1 filter, return favorited field
- i18n: added favorites-related translations (en/zh)
Other:
- Default image model changed from Nano Banana Pro to Nano Banana 2
- providers/models/route.ts: skip media provider types in chat model selector
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
