feat(slint): extend scroll-position restore to all views

Wire the per-history-entry scroll memory (added for Local Library) into
every top-level view: Home/Discover, Album, Local Album, Artist, Musician,
Label, Label Releases, Location, Favorites, Mix, Playlist, Playlist Manager,
Offline Manager, Search, Settings.

Each view's primary scroll container reports its viewport-y and restores it
on back/forward via NavState.restore-scope (scope_for in main.rs maps each
entry to a stable id; tab views carry the tab, e.g. "fav:albums"). The
container restores once per arm, only after content lays out, then clears
the scope. A `changed sr-armed` trigger covers views that persist across
sub-tab navigation (Home's Discover tabs, Favorites' shared list, Playlist
A->B->A) where no fresh mount occurs.

ScrollView-based views (Offline Manager, Settings) use visible-height for
the overflow check; ListView/Flickable views use height. Favorites' shared
albums/artists/playlists/labels Flickable matches the active tab's scope
dynamically.

cc

crates/qbz-slint/ui/search/SearchResultsView.slint

@@ -8,7 +8,7 @@
 // per-type tabs show the full loaded set as a card grid or row list with
 // a load-more button.
 
-import { SearchState, SearchActions, TrackItem, SearchPlaylistItem, AlbumCardItem, SlimItem, DragState } from "../state.slint";
+import { SearchState, SearchActions, TrackItem, SearchPlaylistItem, AlbumCardItem, SlimItem, DragState, NavState } from "../state.slint";
 import { Theme } from "../foundation/semantic-colors.slint";
 import { Typography } from "../foundation/typography.slint";
 import { Radius } from "../foundation/radius.slint";
@@ -436,6 +436,18 @@ export component SearchResultsView inherits Rectangle {
             vertical-stretch: 1;
             viewport-width: self.width;
             viewport-height: body.preferred-height;
+            // Scroll-position restore on back/forward (see nav::scope_for).
+            property <string> sr-armed: NavState.restore-scope;
+            function sr-restore() {
+                if (NavState.restore-scope == "search" && self.viewport-height > self.height) {
+                    self.viewport-y = NavState.scroll-restore;
+                    NavState.restore-scope = "";
+                }
+            }
+            init => { self.sr-restore(); }
+            changed sr-armed => { self.sr-restore(); }
+            changed viewport-height => { self.sr-restore(); }
+            changed viewport-y => { NavState.report-scroll(self.viewport-y); }
 
             body := VerticalLayout {
                 padding-left: 32px;