feat(slint): wire track context-menu actions (favorite/radio/share/playlist/nav)

Connects the previously-inert track context-menu items now that the
backends exist:

  - Add to library -> add_favorite("track").
  - Go to album / Go to artist -> resolve the track (get_track) to its
    album / performer and navigate there.
  - Create radio -> Qobuz track radio (new get_radio_track core wrapper
    over the existing qbz-qobuz endpoint + playback::play_track_radio).
  - Share Qobuz link -> https://www.qobuz.com/track/{id} to clipboard
    (new arboard dep + share module).
  - Share Song.link -> Odesli (api.song.link) pageUrl resolution to
    clipboard.
  - Add to playlist -> a global picker modal (PlaylistPickerModal +
    PlaylistPickerState/Actions + playlist_picker controller) listing
    the user's playlists; picking one calls add_tracks_to_playlist.

Add to mixtape / Make available offline / Track info stay unwired
(no backend yet).

cc

crates/qbz-slint/Cargo.toml

@@ -30,6 +30,7 @@ reqwest = { workspace = true }
 image = { version = "0.25", default-features = false, features = ["jpeg", "png"] }
 urlencoding = "2"
 open = "5"
+arboard = "3"
 rfd = { version = "0.15", default-features = false, features = ["xdg-portal", "tokio"] }
 serde = { workspace = true }
 serde_json = { workspace = true }