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/experimental/testmode/context.d.ts

@@ -0,0 +1,11 @@
+export interface TestReqInfo {
+    url: string;
+    proxyPort: number;
+    testData: string;
+}
+export interface TestRequestReader<R> {
+    url(req: R): string;
+    header(req: R, name: string): string | null;
+}
+export declare function withRequest<R, T>(req: R, reader: TestRequestReader<R>, fn: () => T): T;
+export declare function getTestReqInfo<R>(req?: R, reader?: TestRequestReader<R>): TestReqInfo | undefined;