feat: migrate landing page from Next.js to Astro

Replaces the heavy Next.js SSR app with Astro static site:
- Zero JS shipped for static pages (hero, community, CTA, footer)
- Server-side data fetching in Astro frontmatter (events, hackathon, testimonials)
- Only 4 React islands for interactive parts (mobile menu, roadmap voting, testimonials home, feature request)
- Google Fonts via <link> instead of next/font
- Nix build changed from Node.js systemd service to static nginx (mkStaticAppModule)
- npmDepsHash needs update (set to fake hash, CI will provide correct one)

Performance gains:
- No Node.js server process needed (was using ~10MB RAM)
- No Next.js runtime JS (~200KB+ saved)
- No framer-motion bundle (~130KB saved)
- Static HTML served directly by nginx

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/landing/src/pages/roadmap.astro

@@ -0,0 +1,24 @@
+---
+import Public from '../layouts/Public.astro';
+import RoadmapVote from '../components/RoadmapVote';
+import RequestFeature from '../components/RequestFeature';
+---
+
+<Public title="Roadmap - IMPHNEN">
+  <div class="pt-4 md:pt-6 pb-56 bg-gray-50 min-h-screen mx-4 lg:mx-0">
+    <!-- Feature Request CTA -->
+    <div class="bg-primary-500 rounded-xl px-4 py-8 md:p-8 mb-8 text-center mx-auto max-w-7xl">
+      <div class="max-w-3xl mx-auto">
+        <h1 class="text-2xl md:text-3xl font-bold text-white mb-3">
+          Punya Ide Bagus untuk IMPHNEN?
+        </h1>
+        <p class="text-white/90 mb-6 text-lg text-balance">
+          Bagikan ide fitur yang kamu inginkan dan vote untuk membuatnya nyata!
+        </p>
+        <RequestFeature client:idle />
+      </div>
+    </div>
+
+    <RoadmapVote client:visible />
+  </div>
+</Public>