refactor(slint): rename the Favorites nav-toolbar setting label to Library

Qobuz parity with the renamed favorites header; avoids leaving the old
"Favorites" wording behind (will be revisited during the settings wiring).

cc

crates/qbz-slint/ui/settings/AppearanceSettings.slint

@@ -470,7 +470,7 @@ export component AppearanceSettings inherits VerticalLayout {
     }
     SettingRow {
         unsupported: true;
-        label: @tr("Favorites");
+        label: @tr("Library");
         enabled: !root.tb-locked;
         QbzToggle {
             checked: AppearanceState.nav-tb-favorites;