Major update since basic Spotify playlist injection:
Added web UI for admin dashboard with playlist management, track matching,
and manual mapping controls. Lyrics system with prefetching, caching, and
manual ID mapping. Manual track mapping for missing tracks with persistent
storage. Memory leak fixes and performance improvements. Security hardening
with admin endpoints on internal port. Scrobbling fixes and session cleanup.
HiFi API integration with automatic failover. Playlist cache pre-building
for instant loading. Three-color progress bars showing local/external/missing
track counts.
