feat: add account settings route and user menu dropdown

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/components/Layout.tsx

@@ -55,6 +55,14 @@ export function Layout() {
     return { label };
   });
 
+  const userMenuItems = [
+    {
+      label: 'Account Settings',
+      icon: <Settings size={14} />,
+      onClick: () => navigate('/settings/account'),
+    },
+  ];
+
   const sidebar = (
     <Sidebar collapsed={false} onCollapseToggle={() => {}}>
       <Sidebar.Header
@@ -249,6 +257,7 @@ export function Layout() {
       <TopBar
         breadcrumb={breadcrumb}
         user={username ? { name: username } : undefined}
+        userMenuItems={userMenuItems}
         onLogout={logout}
       />
       <Outlet />