feat(slint): local album homologation, Recently Played fixes, local artist nav

Album view (local/Plex):
- Rebuild LocalAlbumView as a near copy of the Qobuz AlbumPageView (whole-page
  scroll, 224px cover, action row, toolbar with quality badge + track search,
  column header, source-aware rows) minus the label/awards sidebar and Qobuz
  context menus. Add a per-album client-side track search.

Recently Played (Home) — D:
- Carry the track source (qobuz|plex|local) through the recently-played store so
  the cards resolve source-aware artwork (PlexThumb / local file), the album-card
  play routes to local/Plex playback instead of the empty Qobuz path, and the
  card click opens the right album view.
- Fix a regression from the Plex version split: local_queue_track now derives the
  content-hash plex_album_key for album_id (navigation) while album_group_key keeps
  the per-edition split key, so "go to album" and recent Plex albums open correctly.

Local artist navigation — B:
- Implement open_artist (was a TODO): latch the requested artist and select it once
  the Artists tab loads. The shared open-artist is now source-aware (numeric id ->
  Qobuz artist; name -> LocalLibrary Artists tab). Wire the LocalAlbum header artist
  link and the now-playing "Go to artist" for Plex/local.

Folder delete -> Recently Played cascade:
- Removing a Local Library folder now also prunes its albums/tracks from the
  recently-played store (album_keys_in_folder + recently::prune_albums).

Covers — C:
- Robust on-disk folder cover lookup (cover/folder/front/art/<album>.jpg, any image
  as a last resort), shared by the Folders subcards and now-playing/album rows.

cc

crates/qbz-slint/ui/shell/AppShell.slint

@@ -175,7 +175,11 @@ export component AppShell inherits Rectangle {
                     }
                 }
                 // Dedicated Local Library album detail (separate from AlbumView).
-                if NavState.view == ContentView.local-album: LocalAlbumView { }
+                if NavState.view == ContentView.local-album: LocalAlbumView {
+                    open-artist(name) => {
+                        root.open-artist(name);
+                    }
+                }
                 if NavState.view == ContentView.artist: ArtistPageView {
                     open-album(id) => {
                         root.open-album(id);