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/theme.rs

@@ -0,0 +1,88 @@
+use gtk4::prelude::*;
+use gtk4::CssProvider;
+
+const CSS: &str = r#"
+window {
+    background-color: #2e3440;
+    color: #eceff4;
+}
+
+.sidebar {
+    background-color: #3b4252;
+    border-right: 1px solid #434c5e;
+}
+
+.sidebar row {
+    padding: 8px 12px;
+    color: #d8dee9;
+}
+
+.sidebar row:selected {
+    background-color: #5e81ac;
+    color: #eceff4;
+}
+
+.sidebar .section-header {
+    padding: 12px 12px 4px 12px;
+    font-size: 0.75em;
+    font-weight: bold;
+    color: #616e88;
+    text-transform: uppercase;
+    letter-spacing: 1px;
+}
+
+.view-content {
+    padding: 24px;
+}
+
+.view-content label.title {
+    font-size: 1.4em;
+    font-weight: bold;
+    color: #eceff4;
+    margin-bottom: 16px;
+}
+
+button {
+    background-color: #5e81ac;
+    color: #eceff4;
+    border: none;
+    border-radius: 4px;
+    padding: 6px 16px;
+}
+
+button:hover {
+    background-color: #81a1c1;
+}
+
+button.destructive-action {
+    background-color: #bf616a;
+}
+
+button.destructive-action:hover {
+    background-color: #d08770;
+}
+
+entry {
+    background-color: #434c5e;
+    color: #eceff4;
+    border: 1px solid #4c566a;
+    border-radius: 4px;
+}
+
+textview {
+    background-color: #272c36;
+    color: #a3be8c;
+    font-family: monospace;
+    padding: 8px;
+}
+"#;
+
+pub fn load(display: &gtk4::gdk::Display) {
+    let provider = CssProvider::new();
+    provider.load_from_string(CSS);
+    gtk4::style_context_add_provider_for_display(
+        display,
+        &provider,
+        gtk4::STYLE_PROVIDER_PRIORITY_APPLICATION,
+    );
+}