The playlist import picker now also accepts .m3u/.m3u8; EXTINF entries
feed the same Deezer enrichment pipeline as CSV. Collection screens
(wishlist, loved, playlists) gain an export action that resolves each
track to its local file, writes SAF entries relative to the download
tree root so external players and DAP copies resolve them, skips
tracks without a file, and shares the .m3u8 via the system sheet.
Enable strict-casts, strict-inference, and strict-raw-types in
analysis_options.yaml. Add custom_lint with riverpod_lint. Fix all
resulting type warnings with explicit type parameters and safer casts.
Also improves APK update checker to detect device ABIs for correct
variant selection and fixes Deezer artist name parsing edge case.