feat(NotFound): add 404 page with navigation back to home

app/not-found.tsx

@@ -0,0 +1,21 @@
+import Link from "next/link";
+
+export default function NotFound() {
+    return (
+        <div className="top-80 flex items-center justify-center px-4 absolute w-screen">
+            <div className="text-center">
+                <h1 className="text-6xl md:text-8xl font-bold mb-4">404</h1>
+                <h2 className="text-2xl md:text-4xl font-semibold mb-4">Page Not Found</h2>
+                <p className="text-gray-400 mb-8 text-lg">
+                    Sorry, the page you're looking for doesn't exist.
+                </p>
+                <Link
+                    href="/"
+                    className="inline-block px-6 py-3 bg-white text-black font-semibold rounded hover:bg-gray-200 transition-colors"
+                >
+                    Back to Home
+                </Link>
+            </div>
+        </div>
+    );
+}