Add under construction message below hero section

- Add centered construction message with neutral text color
- Wrap components in main element with black background

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Co-Authored-By: Claude <209825114+claude[bot]@users.noreply.github.com>

Author: dtinth

src/pages/index.astro

@@ -4,5 +4,10 @@ import Layout from "../layouts/Layout.astro";
 ---
 
 <Layout>
-  <HeroSection />
+  <main class="bg-black">
+    <HeroSection />
+    <section class="py-16 text-center">
+      <p class="text-neutral-600 text-xl">Website is under construction</p>
+    </section>
+  </main>
 </Layout>