docs: update to next 15 + eslint 9 (#9839)

* update next

* updated react

* update eslint

* finish updating eslint

* fix content lint errors

* fix docs test

* fix vale action

* fix installation errors

www/apps/api-reference/next.config.mjs

@@ -1,10 +1,12 @@
-import mdx from "@next/mdx"
+import createMDX from "@next/mdx"
 import bundleAnalyzer from "@next/bundle-analyzer"
 import rehypeMdxCodeProps from "rehype-mdx-code-props"
 import rehypeSlug from "rehype-slug"
 
 /** @type {import('next').NextConfig} */
 const nextConfig = {
+  // Configure `pageExtensions` to include MDX files
+  pageExtensions: ["js", "jsx", "mdx", "ts", "tsx"],
   basePath: process.env.NEXT_PUBLIC_BASE_PATH || "/api",
   webpack: (config) => {
     config.ignoreWarnings = [{ module: /node_modules\/keyv\/src\/index\.js/ }]
@@ -23,8 +25,7 @@ const nextConfig = {
   },
 }
 
-const withMDX = mdx({
-  extension: /\.mdx?$/,
+const withMDX = createMDX({
   options: {
     rehypePlugins: [
       [
@@ -43,4 +44,4 @@ const withBundleAnalyzer = bundleAnalyzer({
   enabled: process.env.ANALYZE_BUNDLE === "true",
 })
 
-export default withBundleAnalyzer(withMDX(nextConfig))
+export default withMDX(nextConfig)