fix(deps): update astro monorepo to v6

Author: renovate[bot]

package.json

@@ -13,7 +13,7 @@
   },
   "dependencies": {
     "@astrojs/sitemap": "^3.2.1",
-    "astro": "^5.1.1",
+    "astro": "^6.0.0",
     "sharp": "^0.33.5"
   },
   "devDependencies": {