Lands the playlist-append capability end-to-end. Repository does
optimistic Room write at MAX(position)+1 + REST + MutationQueue
fallback (PLAYLIST_APPEND kind from the previous commit). Sheet
lists user-owned playlists for the menu's "Add to playlist…" item;
not yet reachable from a user surface — TrackActionsSheet wires it
in a later commit.
Also adds maxPosition + insertOrIgnore to CachedPlaylistTrackDao
to support the optimistic write.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen
dd42bd5121