feat: gallery masonry layout, favorites system, left-right detail dialog, bump v0.17.0

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>

src/components/settings/ProviderManager.tsx

@@ -264,7 +264,7 @@ const GEMINI_IMAGE_MODELS = [
   { value: 'gemini-2.5-flash-image', label: 'Nano Banana' },
 ];
 
-const DEFAULT_GEMINI_IMAGE_MODEL = 'gemini-3-pro-image-preview';
+const DEFAULT_GEMINI_IMAGE_MODEL = 'gemini-3.1-flash-image-preview';
 
 function getGeminiImageModel(provider: ApiProvider): string {
   try {