feat(admin): scaffold admin routes and base layout

Author: asiansnoodle

src/app/admin/layout.tsx

@@ -0,0 +1,14 @@
+import React from "react";
+
+export default function AdminLayout({
+  children,
+}: Readonly<{
+  children: React.ReactNode;
+}>) {
+  return (
+    <section className="min-h-screen flex bg-neutral-50 text-neutral-900 dark:bg-neutral-950 dark:text-neutral-100">
+      {/* Navbar will go here soon */}
+      <div className="flex-1 p-6">{children}</div>
+    </section>
+  );
+}