feat: restructure Home component layout and add ThemePicker

src/app/home/page.tsx

@@ -1,10 +1,14 @@
 import { Logout } from '@/components/user/sso-logout-button';
+import { ThemePicker } from '@/components/user/theme-picker';
 
 export default function Home() {
   return (
-    <div>
-      <h1>Home</h1>
-      <Logout />
+    <div className='flex flex-col items-center justify-center h-screen'>
+      <div className='absolute top-4 right-4'>{<ThemePicker />}</div>
+      <div>
+        <h1>Home</h1>
+        <Logout />
+      </div>
     </div>
   );
 }