Split Downloads page into main list (left) and batch panel (right).
Each active batch gets a color-coded card with artwork thumbnail,
progress bar, per-track status with download percentages, and
expandable track list. Download rows get matching color indicators.
- Click batch name to open its download/wishlist modal
- Filter icon narrows main list to one batch with clear banner
- Collapsible panel toggle for full-width list view
- Completed batches fade out after 15 seconds
- 7-day batch history with source type color dots
- Artwork fallback shows colored initial when no art available
- Per-track progress: download %, spinner for searching, proc label
- source_page column on sync_history for UI origin tracking
- /api/downloads/all includes batch summaries and per-track progress
- /api/downloads/batch-history endpoint for history queries
- Responsive layout, overflow-x hidden to prevent scroll flicker