New dashboard section shows recent syncs as scrolling cards with
playlist art, source badge, match percentage bar, and health color.
Click any card to open a detail modal showing every track's match
status, confidence score, album art, and download/wishlist status.
Per-track data is now cached in sync_history.track_results for all
sync paths: server-sync (playlist→media server), download missing
tracks, and wishlist processing. SyncResult carries match_details
from the sync service. Both image URLs and matched track info are
preserved for review.
Features:
- Staggered card entrance animation, delete button on hover
- Filter bar: All/Matched/Unmatched/Downloaded
- Color-coded confidence badges (green/amber/red)
- Unmatched tracks show "→ Wishlist" status
- 32px album art thumbnails per track row
- Auto-refreshes every 30 seconds on dashboard
- Falls back gracefully for old syncs without track_results
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