fix(deps): update astro to v5.15.6 [security]

Author: renovate[bot]

package.json

@@ -53,7 +53,7 @@
     "@octokit/openapi-types": "27.0.0",
     "@tailwindcss/vite": "4.1.17",
     "accessible-astro-components": "5.0.2",
-    "astro": "5.15.5",
+    "astro": "5.15.6",
     "astro-icon": "1.1.5",
     "date-fns": "4.1.0",
     "marked": "17.0.0",