build(deps): bump astro from 5.18.1 to 6.1.6 in /site (#551)

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.18.1 to 6.1.6.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/astro/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/astro@6.1.6/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 6.1.6
  dependency-type: direct:production
...

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site/package.json

@@ -14,7 +14,7 @@
     "@iconify-json/lucide": "^1.2.102",
     "@rollup/plugin-yaml": "^4.0.0",
     "@tailwindcss/vite": "^4.2.2",
-    "astro": "^5.0.0",
+    "astro": "^6.1.6",
     "astro-icon": "^1.0.0",
     "js-yaml": "^4.1.0",
     "pagefind": "^1.0.0",