feat: add Users tab with split-pane layout, inline create, detail panel

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

ui/src/pages/Admin/RbacPage.tsx

@@ -2,10 +2,10 @@ import { useState } from 'react';
 import { StatCard, Tabs } from '@cameleer/design-system';
 import { useRbacStats } from '../../api/queries/admin/rbac';
 import styles from './UserManagement.module.css';
+import UsersTab from './UsersTab';
 import GroupsTab from './GroupsTab';
 import RolesTab from './RolesTab';
 
-
 export default function RbacPage() {
   const { data: stats } = useRbacStats();
   const [tab, setTab] = useState('users');