Linthra 0.1.3 — Local music overhaul.

Added:
- Reliable local music access on Android, including SD cards and folders
  picked through the system file chooser.
- Local tracks indexed by title, artist, album, duration, and track number
  for a tidy, correctly ordered library.
- Embedded cover art for local tracks that carry it.
- Synced lyrics for local tracks from a matching ".lrc" or ".txt" file kept
  next to the song.

Changed:
- Clearer Local music settings, with music sources grouped together.
- A clearer scan summary, with guidance when a folder has no playable music.
- Lighter synced-lyrics highlighting and queue sheet, for better battery and
  performance.

Fixed:
- Switching the default playback source no longer breaks fallback for
  Navidrome/Subsonic tracks already in the queue.

Maintenance:
- Documentation updates.

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