feat: update landing app with shadcnI integration

apps/landing/src/app/page.tsx

@@ -1,3 +1,10 @@
+import { Button } from '@imphnen-frontend-service/shadcn-ui/atoms';
+
 export default function Page() {
-  return <></>;
+  return (
+    <>
+      <h1 className="text-2xl underline">Hello World</h1>
+      <Button>Click Me</Button>
+    </>
+  );
 }