update: previews now use real posters from your library
feat: Add preview functionality to web UI
Add Preview page with badge type and poster selection
Implement preview API endpoints for badge generation
Support all badge types (audio, resolution, review, awards)
Allow light/dark example poster selection
Generate previews with mock data (no upload/metadata)
Real-time job status polling for preview completion
Reorder menu items (Dashboard → Execute → Schedules → Preview → Settings)