feat(slint): recently-played albums section on Discover Home

Discover Home now has both recently-played modules: a carousel of
album cards and the slim track grid (renamed "Recently Played
Tracks").

- recently.rs records track plays with their album metadata;
  load_albums() derives the distinct recent albums from that history
- home.rs threads a recent_albums list into HomeData; HomeView renders
  it as a carousel; the artwork pipeline gains ArtworkTarget::RecentAlbum

Also raises the header-gradient contrast: the artwork color is now
saturation-boosted off its average and normalized to a fixed peak
brightness instead of just darkened, so the tint is actually visible.

cc

crates/qbz-slint/ui/discover/HomeView.slint

@@ -188,8 +188,21 @@ export component HomeView inherits Rectangle {
                     }
                 }
 
+                if HomeState.recent-albums.length > 0: Carousel {
+                    section: {
+                        title: @tr("Recently Played Albums"),
+                        albums: HomeState.recent-albums,
+                    };
+                    album-clicked(id) => {
+                        root.album-clicked(id);
+                    }
+                    media-action(kind, id, action) => {
+                        root.media-action(kind, id, action);
+                    }
+                }
+
                 if HomeState.recent.length > 0: GridSection {
-                    title: @tr("Recently Played");
+                    title: @tr("Recently Played Tracks");
                     items: HomeState.recent;
                     item-clicked(id) => {
                         root.media-action("track", id, "play");

crates/qbz-slint/ui/state.slint

@@ -38,6 +38,7 @@ export global HomeState {
     in property <[DiscoverSection]> sections: [];
     in property <[SlimItem]> popular: [];
     in property <[SlimItem]> recent: [];
+    in property <[AlbumCardItem]> recent-albums: [];
     in property <bool> loading: false;
 }
 
@@ -59,6 +60,10 @@ export global AlbumState {
     in property <string> artist-id;
     in property <string> info-line;
     in property <string> quality-tier;
+    // "24-bit / 96 kHz" — quality-badge detail line.
+    in property <string> quality-detail;
+    // Editorial description / review (HTML stripped). May be empty.
+    in property <string> description;
     in property <image> artwork;
     // Artwork-derived tint for the header gradient.
     in property <color> header-color: #181820;