feat(ui): refine Graphite visuals and center navigation content

shell/ferese-settings/src/visuals.rs

@@ -61,6 +61,38 @@ pub fn panel_select<'a>(
     cosmic::widget::container(content).class(surface(ferese_theme::mix(p.card, p.text, 0.035), 7.))
 }
 
+/// Low-contrast section planes replace large filled cards. High contrast
+/// preferences strengthen boundaries without changing the section hierarchy.
+pub fn section(p: Palette) -> cosmic::theme::Container<'static> {
+    cosmic::theme::Container::custom(move |_| cosmic::widget::container::Style {
+        background: Some(ferese_theme::mix(p.background, p.card, 0.42).into()),
+        border: cosmic::iced::Border {
+            width: 1.,
+            color: ferese_theme::mix(
+                p.background,
+                p.text,
+                if p.high_contrast { 0.45 } else { 0.09 },
+            ),
+            radius: p.radius.min(10.).into(),
+            shape: cosmic::iced::border::Shape::Continuous,
+            ..Default::default()
+        },
+        ..Default::default()
+    })
+}
+pub fn sidebar(p: Palette) -> cosmic::theme::Container<'static> {
+    cosmic::theme::Container::custom(move |_| cosmic::widget::container::Style {
+        background: Some(p.sidebar.into()),
+        border: cosmic::iced::Border {
+            width: 1.,
+            color: ferese_theme::mix(p.sidebar, p.text, if p.high_contrast { 0.45 } else { 0.07 }),
+            radius: 0.into(),
+            ..Default::default()
+        },
+        ..Default::default()
+    })
+}
+
 pub fn color(value: &str, fallback: Color) -> Color {
     ferese_theme::parse_color(value).unwrap_or(fallback)
 }
@@ -86,7 +118,7 @@ pub fn brand_icon() -> svg_icon::Icon {
     cosmic::widget::icon::from_svg_bytes(ferese_theme::icons::APPLICATION)
         .symbolic(false)
         .icon()
-        .size(32)
+        .size(24)
         .content_fit(cosmic::iced::ContentFit::Contain)
 }