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/tsconfig.json

@@ -1,48 +1,12 @@
 {
-  "extends": "../../tsconfig.base.json",
+  "extends": "astro/tsconfigs/strict",
   "compilerOptions": {
-    "jsx": "preserve",
-    "strict": true,
-    "noEmit": true,
-    "emitDeclarationOnly": false,
-    "esModuleInterop": true,
-    "target": "ES2022",
-    "module": "esnext",
-    "moduleResolution": "bundler",
-    "resolveJsonModule": true,
-    "isolatedModules": true,
-    "lib": ["dom", "dom.iterable", "esnext"],
-    "allowJs": true,
-    "allowSyntheticDefaultImports": true,
-    "forceConsistentCasingInFileNames": true,
-    "incremental": true,
-    "plugins": [
-      {
-        "name": "next"
-      }
-    ],
+    "jsx": "react-jsx",
+    "jsxImportSource": "react",
     "baseUrl": ".",
     "paths": {
-      "@components": ["../../libs/ui/src/atoms/index.ts"],
-      "@utils": ["../../libs/utils/src/tailwind-merge/index.ts"],
-      "@schemas": ["../../libs/service/src/schemas/index.ts"],
       "@/*": ["src/*"],
-      "@imphnen-frontend-service/service": ["../../libs/service/src/index.ts"],
-      "@imphnen-frontend-service/ui/atoms": ["../../libs/ui/src/atoms/index.ts"],
-      "@imphnen-frontend-service/ui/molecules": ["../../libs/ui/src/molecules/index.ts"],
-      "@imphnen-frontend-service/ui/organisms": ["../../libs/ui/src/organisms/index.ts"],
-      "@imphnen-frontend-service/utils": ["../../libs/utils/src/index.ts"]
+      "@data/*": ["src/data/*"]
     }
-  },
-  "include": [
-    "**/*.js",
-    "**/*.jsx",
-    "**/*.ts",
-    "**/*.tsx",
-    "../../apps/landing/.next/types/**/*.ts",
-    "../../dist/apps/landing/.next/types/**/*.ts",
-    "next-env.d.ts",
-    ".next/types/**/*.ts"
-  ],
-  "exclude": ["node_modules", "jest.config.ts", "**/*.spec.ts", "**/*.test.ts"]
+  }
 }