feat: add auth

app/(auth)/layout.tsx

@@ -0,0 +1,16 @@
+/**
+ * Shared layout for the auth pages (login, signup, forgot-password,
+ * reset-password). Provides the centered card frame so each page only
+ * has to render its own form.
+ */
+export default function AuthLayout({
+  children,
+}: {
+  children: React.ReactNode;
+}) {
+  return (
+    <main className="flex items-center justify-center px-4 py-12 min-h-[90vh]">
+      <div className="w-full max-w-md">{children}</div>
+    </main>
+  );
+}