feat(app): persist customization settings

ui/app.js

@@ -136,6 +136,31 @@ function wireVaultActions() {
   if (button) button.addEventListener('click', saveDemoVault);
 }
 
+async function loadAppConfig() {
+  return invokeOrFallback('load_app_config', { theme_id: 'rabby-light', restore_workspace: true, profiles: [], shortcuts: [] });
+}
+
+async function saveSettings() {
+  const theme = document.getElementById('theme-select').value;
+  const output = document.getElementById('settings-status');
+  output.textContent = 'Saving settings…';
+  try {
+    const tauri = window.__TAURI__?.core;
+    if (!tauri) throw new Error('Tauri bridge unavailable in browser preview');
+    const config = await loadAppConfig();
+    config.theme_id = theme;
+    const saved = await tauri.invoke('save_app_config', { config, path: null });
+    output.textContent = `Saved ${saved.theme_id}`;
+  } catch (error) {
+    output.textContent = String(error);
+  }
+}
+
+function wireSettingsActions() {
+  const button = document.getElementById('save-settings');
+  if (button) button.addEventListener('click', saveSettings);
+}
+
 async function runLocalTerminalCommand() {
   const command = document.getElementById('terminal-command').value;
   const output = document.getElementById('terminal-output');
@@ -168,6 +193,7 @@ async function boot() {
   renderDashboard(dashboard);
   renderFeatures(features);
   wireVaultActions();
+  wireSettingsActions();
   wireTerminalActions();
 }