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/gray-matter/lib/defaults.js

@@ -0,0 +1,18 @@
+'use strict';
+
+const engines = require('./engines');
+const utils = require('./utils');
+
+module.exports = function(options) {
+  const opts = Object.assign({}, options);
+
+  // ensure that delimiters are an array
+  opts.delimiters = utils.arrayify(opts.delims || opts.delimiters || '---');
+  if (opts.delimiters.length === 1) {
+    opts.delimiters.push(opts.delimiters[0]);
+  }
+
+  opts.language = (opts.language || opts.lang || 'yaml').toLowerCase();
+  opts.engines = Object.assign({}, engines, opts.parsers, opts.engines);
+  return opts;
+};