feat: add Vista-style 404 page

components/go-back-button.tsx

@@ -0,0 +1,15 @@
+"use client";
+
+import { useRouter } from "next/navigation";
+
+export default function GoBackButton() {
+  const router = useRouter();
+  return (
+    <button
+      onClick={() => router.back()}
+      className="px-4 py-1.5 text-sm bg-gradient-to-b from-blue-100 to-blue-200 border border-blue-300 rounded hover:from-blue-200 hover:to-blue-300 transition-colors"
+    >
+      ← Go Back
+    </button>
+  );
+}