Update react monorepo to v19

Author: renovate[bot]

package.json

@@ -57,8 +57,8 @@
     "gatsby-transformer-sharp": "^5.0.0",
     "mdx-embed": "^1.1.2",
     "prop-types": "^15.8.1",
-    "react": "^18.0.0",
-    "react-dom": "18.3.1",
+    "react": "^19.0.0",
+    "react-dom": "19.2.3",
     "react-helmet": "6.1.0",
     "react-typography": "0.16.23",
     "remark-gfm": "^3.0.0",