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/lib/build-custom-route.d.ts

@@ -0,0 +1,5 @@
+import type { ManifestHeaderRoute, ManifestRedirectRoute, ManifestRewriteRoute } from '../build';
+import { type Header, type Redirect, type Rewrite } from './load-custom-routes';
+export declare function buildCustomRoute(type: 'header', route: Header): ManifestHeaderRoute;
+export declare function buildCustomRoute(type: 'rewrite', route: Rewrite): ManifestRewriteRoute;
+export declare function buildCustomRoute(type: 'redirect', route: Redirect, restrictedRedirectPaths: string[]): ManifestRedirectRoute;