fix(deps): Update dependency astro to v6

Author: renovate[bot]

package.json

@@ -16,7 +16,7 @@
   "dependencies": {
     "@astrojs/check": "^0.9.4",
     "@astrojs/starlight": "^0.37.0",
-    "astro": "^5.9.4",
+    "astro": "^6.0.0",
     "globals": "^17.0.0",
     "sharp": "^0.34.2",
     "typescript": "^5.9.2"