fix(slint): favorites covers stayed grey under sort/group

The artwork pipeline wrote a decoded cover into the SOURCE model
(FavoritesState.albums / .tracks) by index, but the views render the
derived albums-visible / albums-grouped / tracks-visible models, which
are independent clones whenever a sort/group/search is active. So a
late-arriving cover never reached the rendered card (grey until a
re-derive). Add favorites::set_album_artwork / set_track_artwork to also
propagate the cover by id into the rendered model(s); apply_artwork calls
them for FavoriteAlbum / FavoriteTrack. The disk cache was already in use;
this was purely the render target.

cc

crates/qbz-slint/src/artwork.rs

@@ -502,15 +502,22 @@ fn apply_artwork(
         ArtworkTarget::FavoriteTrack { index } => {
             let model = window.global::<crate::FavoritesState>().get_tracks();
             if let Some(mut item) = model.row_data(index) {
-                item.artwork = image;
+                item.artwork = image.clone();
+                let id = item.id.to_string();
                 model.set_row_data(index, item);
+                // Also reach the rendered (possibly sorted/grouped) model.
+                crate::favorites::set_track_artwork(window, &id, image);
             }
         }
         ArtworkTarget::FavoriteAlbum { index } => {
             let model = window.global::<crate::FavoritesState>().get_albums();
             if let Some(mut item) = model.row_data(index) {
-                item.artwork = image;
+                item.artwork = image.clone();
+                let id = item.id.to_string();
                 model.set_row_data(index, item);
+                // Also reach the rendered visible/grouped model (clones when
+                // a sort/group is active — they don't share `albums`).
+                crate::favorites::set_album_artwork(window, &id, image);
             }
         }
         ArtworkTarget::DiscoverBrowseAlbum { index } => {

crates/qbz-slint/src/favorites.rs

@@ -791,6 +791,53 @@ pub fn remove_album_row(window: &AppWindow, id: &str) {
     }
 }
 
+// ---- Artwork propagation -----------------------------------------------
+// The artwork pipeline writes a decoded cover into the SOURCE model
+// (`albums` / `tracks`) by index, but the views render the derived
+// `albums-visible` / `albums-grouped` / `tracks-visible` models, which are
+// independent clones whenever a sort / group / search is active. So a
+// late-arriving cover never reached the rendered card (it stayed grey
+// until a re-derive). Propagate it into the rendered model(s) by id too.
+
+fn set_artwork_in_albums(model: &ModelRc<AlbumCardItem>, id: &str, image: &slint::Image) {
+    for i in 0..model.row_count() {
+        if let Some(mut item) = model.row_data(i) {
+            if item.id.as_str() == id {
+                item.artwork = image.clone();
+                model.set_row_data(i, item);
+                break;
+            }
+        }
+    }
+}
+
+/// Set a freshly-decoded album cover (by id) on the rendered favorites
+/// album models (flat `albums-visible` + every `albums-grouped` section).
+pub fn set_album_artwork(window: &AppWindow, id: &str, image: slint::Image) {
+    let st = window.global::<FavoritesState>();
+    set_artwork_in_albums(&st.get_albums_visible(), id, &image);
+    let grouped = st.get_albums_grouped();
+    for s in 0..grouped.row_count() {
+        if let Some(section) = grouped.row_data(s) {
+            set_artwork_in_albums(&section.albums, id, &image);
+        }
+    }
+}
+
+/// Same for the rendered favorites tracks model (`tracks-visible`).
+pub fn set_track_artwork(window: &AppWindow, id: &str, image: slint::Image) {
+    let model = window.global::<FavoritesState>().get_tracks_visible();
+    for i in 0..model.row_count() {
+        if let Some(mut item) = model.row_data(i) {
+            if item.id.as_str() == id {
+                item.artwork = image.clone();
+                model.set_row_data(i, item);
+                break;
+            }
+        }
+    }
+}
+
 // ---- Tracks multi-select (mirrors playlist.rs) -------------------------
 // Selection lives on TrackItem.selected in the rendered `tracks-visible`
 // model (which shares `tracks` when no search filter is active).