Albums/Artists/Playlists were new keys because the old Flutter strings
were plurals, so their translations went unused. Take the `other` form of
resourcesAlbumName/resourcesArtistName/resourcesPlaylistName into the three
plain-string resources for the 26-27 locales that translated them. Arabic
`resources_album_name` and Hungarian `resources_playlist_name` stay English
because their upstream `other` form is empty.
Move every exposed UI string into res/values/strings.xml (+ plurals) and
read it via stringResource/pluralStringResource or getString, with 27
locale files carried over from the Flutter app's Weblate translations.
Only strings whose English is unchanged reuse an old translation; reworded
ones get fresh keys.
Persisted download failures become a DownloadError enum mapped to string
resources (stored by name, unknown legacy values degrade to Failed), the
per-app locale config is generated by AGP, and StringResourcesTest guards
locale keys and placeholders.
austinried