feat(slint): Label landing page + All Releases sub-view

Port the Tauri LabelView module to native Slint, reusing existing
components and extending where needed (no duplication).

Landing (new LabelPageView): circular header + description read-more +
Follow toggle, sticky JUMP TO bar, Popular Tracks (multi-select, 5->20->50
reveal, Play all), and Releases (+ See all) / Critics' Picks / Playlists /
Artists / More Labels carousels.

All Releases sub-view (LabelReleasesView): circular header + album count,
toolbar (local search, group-by-artist, Hi-Res filter, sort) + grid/list
toggle, load-more, states. TYPE column now populated.

Split the label route: ContentView::label -> LabelPageView (landing),
ContentView::label-releases -> LabelReleasesView; add NavEntry::LabelReleases.
label.rs load_label_page parses /label/page + getAlbums + explore + the
favorite-labels set; derive_releases re-derives the sub-view list.
Reuse Carousel/PlaylistCarousel/ArtistCarousel/TrackRow/AlbumCard/
AlbumListRow/JumpNavBar/QbzSelect/ExpandableSearch; extend ArtistCard/
ArtistCarousel (follow-mode/follow-kind); promote CircleAction to a shared
primitive; JumpNavBar gains show-search. Wire label media-actions:
follow, play-top, open (more-labels), see-all.

cc

crates/qbz-slint/ui/primitives/CircleAction.slint

@@ -0,0 +1,41 @@
+// Ghost circular action button — translucent fill with a faint ring,
+// icon tinted on hover/active (never a solid accent fill, mirroring the
+// Tauri transport controls). Shared by the artist + label page headers
+// and their Popular Tracks clusters (Play all / Select / More).
+
+import { Theme } from "../foundation/semantic-colors.slint";
+import { QbzIcon } from "QbzIcon.slint";
+
+export component CircleAction inherits Rectangle {
+    in property <image> icon;
+    in property <bool> primary: false;
+    // Stays "pressed" — same surface as hover, icon tinted accent.
+    in property <bool> active: false;
+    in property <length> diameter: 40px;
+    callback clicked();
+
+    width: root.diameter;
+    height: root.diameter;
+    border-radius: root.diameter / 2;
+    background: (ta.has-hover || root.active) ? Theme.surface-hover : transparent;
+    border-width: 1px;
+    border-color: (ta.has-hover || root.active) ? Theme.text-disabled : Theme.border-subtle;
+
+    QbzIcon {
+        source: root.icon;
+        width: root.primary ? 19px : 17px;
+        height: root.primary ? 19px : 17px;
+        x: (parent.width - self.width) / 2;
+        y: (parent.height - self.height) / 2;
+        tint: root.active
+            ? Theme.accent
+            : (ta.has-hover ? Theme.text-primary : Theme.text-secondary);
+    }
+
+    ta := TouchArea {
+        mouse-cursor: pointer;
+        clicked => {
+            root.clicked();
+        }
+    }
+}

crates/qbz-slint/ui/primitives/JumpNavBar.slint

@@ -31,6 +31,10 @@ export struct JumpNavTab {
 export component JumpNavBar inherits Rectangle {
     in property <[JumpNavTab]> tabs;
     in property <string> active-tab-id;
+    // Whether the inline page-search affordance is offered. Artist pages
+    // have it; the label page does not (Tauri's label jump-nav has no
+    // search), so the label view passes show-search: false.
+    in property <bool> show-search: true;
     in-out property <bool> search-open: false;
     in-out property <string> search-text;
 
@@ -244,7 +248,7 @@ export component JumpNavBar inherits Rectangle {
         // expanded input run all the way to the bar's right padding
         // (right where the user just clicked the lupa). The inline
         // input carries its own X close button.
-        if !root.search-open: VerticalLayout {
+        if root.show-search && !root.search-open: VerticalLayout {
             alignment: center;
             horizontal-stretch: 0;
             Rectangle {