feat: complete MDX migration, stabilize environment & verify via E2E tests

Former-commit-id: ec3e64156a2e182535cbdcf0d975cd54603a517d

lib/mdx.ts

@@ -0,0 +1,21 @@
+import fs from 'fs';
+import path from 'path';
+import matter from 'gray-matter';
+
+const CONTENT_DIR = path.join(process.cwd(), 'content');
+
+export async function getMdxContent(locale: string, slug: string) {
+  const filePath = path.join(CONTENT_DIR, locale, `${slug}.mdx`);
+  
+  if (!fs.existsSync(filePath)) {
+    return null;
+  }
+
+  const source = fs.readFileSync(filePath, 'utf8');
+  const { content, data } = matter(source);
+
+  return {
+    content,
+    frontmatter: data,
+  };
+}