feat(auth): add layout for authentication pages with redirect logic

src/app/(auth)/layout.tsx

@@ -0,0 +1,41 @@
+import Image from "next/image";
+import { auth } from "@/lib/auth";
+import { Code } from "lucide-react";
+import { redirect } from "next/navigation";
+
+interface AuthLayoutProps {
+  children: React.ReactNode;
+}
+
+export default async function AuthLayout({
+  children
+}: AuthLayoutProps) {
+  const session = await auth();
+  if (session) redirect("/");
+
+  return (
+    <div className="grid min-h-svh lg:grid-cols-2">
+      <div className="flex flex-col gap-4 p-6 md:p-10">
+        <div className="flex justify-center gap-2 md:justify-start">
+          <a href="/" className="flex items-center gap-2 font-medium">
+            <div className="flex h-6 w-6 items-center justify-center rounded-md bg-primary text-primary-foreground">
+              <Code className="size-4" />
+            </div>
+            Judge4c
+          </a>
+        </div>
+        <div className="flex flex-1 items-center justify-center">
+          <div className="w-full max-w-sm">{children}</div>
+        </div>
+      </div>
+      <div className="relative hidden bg-muted lg:block">
+        <Image
+          src="/placeholder.svg"
+          alt="Image"
+          fill
+          className="absolute inset-0 h-full w-full object-cover dark:brightness-[0.2] dark:grayscale"
+        />
+      </div>
+    </div>
+  );
+}