chore(deps): update gatsby monorepo

Author: renovate[bot]

package.json

@@ -73,7 +73,7 @@
     "@types/react-dom": "18.3.7",
     "@vitest/coverage-v8": "3.2.4",
     "@vitest/ui": "3.2.4",
-    "gatsby": "5.14.1",
+    "gatsby": "5.15.0",
     "jsdom": "26.1.0",
     "memfs": "4.36.0",
     "pkgroll": "2.15.3",