fix(slint): drop the reserved horizontal scrollbar gutter on Home

The carousels' clipped, oversized inner track inflated the scroll
content's preferred width, so the vertical ScrollView reserved a
bottom gutter for a horizontal scrollbar that is never shown. Pin the
ScrollView viewport-width to its visible width so horizontal content
can never overflow.

cc

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

@@ -159,8 +159,12 @@ export component HomeView inherits Rectangle {
         }
 
         // --- Scrollable sections -----------------------------------------
-        ScrollView {
+        // viewport-width is pinned to the visible width so the carousels'
+        // clipped (oversized) content never triggers a horizontal scrollbar
+        // or reserves a gutter for one.
+        home-scroll := ScrollView {
             vertical-stretch: 1;
+            viewport-width: home-scroll.visible-width;
             horizontal-scrollbar-policy: ScrollBarPolicy.always-off;
             VerticalLayout {
                 padding: 32px;