Revert "feat(#112): add admin header bar with back button and logout"

This reverts commit a484364029.

ui/src/pages/Admin/AdminLayout.tsx

@@ -1,8 +1,5 @@
 import { Outlet, useNavigate, useLocation } from 'react-router';
 import { Tabs } from '@cameleer/design-system';
-import { ArrowLeft, LogOut } from 'lucide-react';
-import { useAuthStore } from '../../auth/auth-store';
-import styles from './AdminLayout.module.css';
 
 const ADMIN_TABS = [
   { label: 'User Management', value: '/admin/rbac' },
@@ -16,35 +13,15 @@ const ADMIN_TABS = [
 export default function AdminLayout() {
   const navigate = useNavigate();
   const location = useLocation();
-  const { username, logout } = useAuthStore();
-
-  const handleBack = () => navigate('/exchanges');
-  const handleLogout = () => {
-    logout();
-    navigate('/login');
-  };
 
   return (
     <div>
-      <header className={styles.header}>
-        <button className={styles.backBtn} onClick={handleBack}>
-          <ArrowLeft size={16} />
-          Back
-        </button>
-        <span className={styles.title}>Admin</span>
-        <div className={styles.userSection}>
-          <span className={styles.username}>{username}</span>
-          <button className={styles.logoutBtn} onClick={handleLogout}>
-            <LogOut size={14} />
-          </button>
-        </div>
-      </header>
       <Tabs
         tabs={ADMIN_TABS}
         active={location.pathname}
         onChange={(path) => navigate(path)}
       />
-      <div className={styles.content}>
+      <div style={{ padding: '20px 24px 40px' }}>
         <Outlet />
       </div>
     </div>