fix(website): migrate blog from next-mdx-remote to @next/mdx

next-mdx-remote evaluates MDX at runtime with a different React version
than Next.js 16's internal canary, causing build failures. Switch to
@next/mdx which compiles MDX through Next.js's own bundler pipeline.

- Replace next-mdx-remote with @next/mdx, @mdx-js/mdx, @mdx-js/loader
- Use dynamic imports for blog MDX files instead of MDXRemote
- Add remark-frontmatter so compiler skips YAML frontmatter blocks
- Gate cache/CSP headers to production only (immutable dev chunks
  were poisoning browser cache)

Made-with: Cursor

apps/website/next.config.mjs

@@ -1,5 +1,10 @@
+import createMDX from "@next/mdx";
+
+const isProd = process.env.NODE_ENV === "production";
+
 /** @type {import('next').NextConfig} */
 const nextConfig = {
+  pageExtensions: ["ts", "tsx", "md", "mdx"],
   allowedDevOrigins: ["*.ngrok-free.dev"],
   experimental: {
     optimizePackageImports: ["framer-motion", "motion", "gsap", "@gsap/react"],
@@ -11,10 +16,9 @@ const nextConfig = {
    // formats: ["image/avif", "image/webp"],
   },
   async headers() {
+    if (!isProd) return [];
+
     return [
-      // Next.js chunks include a content hash in their filename, so they are
-      // safe to cache indefinitely. Vercel sets this automatically on its CDN,
-      // but the explicit header also covers self-hosted deployments.
       {
         source: "/_next/static/(.*)",
         headers: [
@@ -24,8 +28,6 @@ const nextConfig = {
           },
         ],
       },
-      // Lottie JSON files are large (1.4–2.6 MB each) and change infrequently.
-      // A 1-year cache means repeat visitors skip the expensive re-download.
       {
         source: "/animation/(.*)",
         headers: [
@@ -35,8 +37,6 @@ const nextConfig = {
           },
         ],
       },
-      // Public images: 7-day TTL with a 1-day stale-while-revalidate window
-      // so content updates eventually propagate without blocking visitors.
       {
         source: "/images/(.*)",
         headers: [
@@ -76,4 +76,10 @@ const nextConfig = {
   },
 };
 
-export default nextConfig;
+const withMDX = createMDX({
+  options: {
+    remarkPlugins: ["remark-frontmatter"],
+  },
+});
+
+export default withMDX(nextConfig);