feat(blog): add file-based blog with dynamic slugs, MDX content and layout shell

- Introduced blog routing using Next.js App Router
- Implemented dynamic [slug] pages for blog posts
- Added MDX-based content loading via lib/posts
- Integrated shared TopBar layout with navigation
- Established clear content, lib and component separation

apps/public-web/node_modules/next/dist/server/request/headers.d.ts

@@ -0,0 +1,11 @@
+import { type ReadonlyHeaders } from '../web/spec-extension/adapters/headers';
+/**
+ * This function allows you to read the HTTP incoming request headers in
+ * [Server Components](https://nextjs.org/docs/app/building-your-application/rendering/server-components),
+ * [Server Actions](https://nextjs.org/docs/app/building-your-application/data-fetching/server-actions-and-mutations),
+ * [Route Handlers](https://nextjs.org/docs/app/building-your-application/routing/route-handlers) and
+ * [Middleware](https://nextjs.org/docs/app/building-your-application/routing/middleware).
+ *
+ * Read more: [Next.js Docs: `headers`](https://nextjs.org/docs/app/api-reference/functions/headers)
+ */
+export declare function headers(): Promise<ReadonlyHeaders>;