feat: enhance MDX link component with external link detection

mdx-components.tsx

@@ -30,11 +30,20 @@ export function useMDXComponents(components: MDXComponents): MDXComponents {
       </blockquote>
     ),
     hr: () => <hr className="my-8 border-border" />,
-    a: ({ href, children }) => (
-      <a href={href} className="font-medium underline underline-offset-4 hover:text-accent transition-colors">
-        {children}
-      </a>
-    ),
+    a: ({ href, children, ...props }) => {
+      const isExternal = typeof href === 'string' && (href.startsWith('http://') || href.startsWith('https://'))
+      return (
+        <a
+          href={href}
+          target={isExternal ? '_blank' : undefined}
+          rel={isExternal ? 'noopener noreferrer' : undefined}
+          className="font-medium underline underline-offset-4 hover:text-accent transition-colors"
+          {...props}
+        >
+          {children}
+        </a>
+      )
+    },
     code: ({ children, ...props }) => (
       <code
         {...props}