Scaffold BOS repo: dotfiles, ISO profile, and bos-settings GTK4 app

Implements all four components from the BOS spec:
- dotfiles/: default Hyprland, bread, breadbox, breadcrumbs configs
- iso/: archiso profiledef, package list, Calamares YAML modules, post-install.sh
- bos-settings/: Cargo workspace with GTK4 settings app (8 views: snapshots,
  packages, bread, breadbar, breadbox, breadcrumbs, breadpad, hyprland)

https://claude.ai/code/session_01WszGHvCmxgcyTwNSkfLF9P

bos-settings/src/ui/sidebar.rs

@@ -0,0 +1,66 @@
+use gtk4::prelude::*;
+use gtk4::{Box as GBox, Label, ListBox, ListBoxRow, Orientation, Separator};
+
+pub struct SidebarItem {
+    pub id: &'static str,
+    pub label: &'static str,
+}
+
+pub const APPS_ITEMS: &[SidebarItem] = &[
+    SidebarItem { id: "bread", label: "bread" },
+    SidebarItem { id: "breadbar", label: "breadbar" },
+    SidebarItem { id: "breadbox", label: "breadbox" },
+    SidebarItem { id: "breadcrumbs", label: "breadcrumbs" },
+    SidebarItem { id: "breadpad", label: "breadpad" },
+];
+
+pub const SYSTEM_ITEMS: &[SidebarItem] = &[
+    SidebarItem { id: "snapshots", label: "Snapshots" },
+    SidebarItem { id: "packages", label: "Packages" },
+    SidebarItem { id: "hyprland", label: "Hyprland" },
+];
+
+pub fn build() -> (GBox, ListBox) {
+    let vbox = GBox::new(Orientation::Vertical, 0);
+    vbox.add_css_class("sidebar");
+    vbox.set_width_request(190);
+
+    let list = ListBox::new();
+    list.set_selection_mode(gtk4::SelectionMode::Single);
+    list.add_css_class("sidebar");
+
+    append_section(&list, "Apps", APPS_ITEMS);
+    append_section(&list, "System", SYSTEM_ITEMS);
+
+    // Select first item by default
+    if let Some(first) = list.row_at_index(1) {
+        list.select_row(Some(&first));
+    }
+
+    vbox.append(&list);
+    (vbox, list)
+}
+
+fn append_section(list: &ListBox, title: &str, items: &[SidebarItem]) {
+    // Section header (non-selectable)
+    let header_row = ListBoxRow::new();
+    header_row.set_selectable(false);
+    header_row.set_activatable(false);
+    let header_lbl = Label::new(Some(title));
+    header_lbl.add_css_class("section-header");
+    header_lbl.set_xalign(0.0);
+    header_row.set_child(Some(&header_lbl));
+    list.append(&header_row);
+
+    for item in items {
+        let row = ListBoxRow::new();
+        row.set_widget_name(item.id);
+
+        let lbl = Label::new(Some(item.label));
+        lbl.set_xalign(0.0);
+        lbl.set_margin_top(2);
+        lbl.set_margin_bottom(2);
+        row.set_child(Some(&lbl));
+        list.append(&row);
+    }
+}