feat(docs): Update documentation structure and add metadata titles

- Changed the source configuration to point to the new documentation directory structure.
- Added front matter titles to various documentation files for better organization and SEO.
- Updated multiple markdown files to include titles, enhancing clarity and navigation.

Author: hotlong

apps/site/source.config.ts

@@ -1,7 +1,9 @@
 import { defineConfig, defineDocs } from 'fumadocs-mdx/config';
 
 export const { docs, meta } = defineDocs({
-  dir: 'content/docs',
+  dir: '../../docs',
+  root: '../../docs',
+  files: ['**/*.{md,mdx}', '!**/node_modules/**'],
 });
 
 export default defineConfig();