feat: migrate admin UI to card-based layouts
Replaced table-based layouts with modern card components for better UX:
- Transcriptions tab now uses admin-transcriptions component
- Users tab now uses admin-users component
- Both tabs feature search, filtering, and click-to-view modals
- Removed ~500 lines of duplicate table-rendering code
- Cleaned up CSS (removed table/search/sort styles)
- Simplified JavaScript to just handle stats and modal events
All three admin tabs now have consistent card-based design.
💘 Generated with Crush
Co-Authored-By: Crush <crush@charm.land>