Linthra 0.1.6 — Plex offline caching.

Added:
- Plex tracks can now be downloaded for offline playback, like Jellyfin
  and Navidrome/Subsonic.
- Cached Plex tracks play from your device automatically, and fall back
  to streaming when a cached file is missing or can't be opened.

Changed:
- Offline downloads are now written atomically (download, validate, then
  swap into place), so an interrupted download can't leave a broken file.
- Per-ABI release APKs are built in isolation to match F-Droid's
  reproducible split-APK build.

Notes:
- Plex cached files are keyed to your library item identity and never
  contain your Plex token.

No ads, no tracking, no analytics, no telemetry.
