feat(slint): offline button on every Qobuz track row + cache-whole-playlist
- TrackRow show-download now defaults to true: every Qobuz track row (album,
artist, label, playlist, mix, search, favorites) carries the offline
cloud/check button. Non-Qobuz surfaces (future Local Library / Plex) opt out
by setting it false.
- Playlist header gains a "make offline" CircleAction -> ("playlist","cache")
-> offline_cache::cache_playlist (get_playlist -> batch its tracks), mirroring
the album-header action.
qbz-slint compiles clean.
cc
vicrodh
a7f2283c92