feat: album list, artist list, and artist detail views

- Fav albums: now shows a sortable list (title/artist/year/tracks);
  double-click opens the album
- Fav artists: now shows a sortable list; double-click opens the artist
- Artist detail page: name, biography summary, and their album list
- Rust ArtistDto gains albums field; get_artist fixed to extra=albums only
- Volume popup minimum width set so "100%" label is never clipped

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/widget/volumebutton.hpp

@@ -22,6 +22,7 @@ public:
 
         auto *menu   = new QMenu(this);
         auto *widget = new QWidget(menu);
+        widget->setMinimumWidth(72);
         auto *layout = new QVBoxLayout(widget);
         layout->setContentsMargins(6, 6, 6, 6);