feat: add GitHub link with icon to AppHeader component

frontend/src/components/layout/AppHeader.tsx

@@ -50,6 +50,19 @@ export const AppHeader: React.FC<AppHeaderProps> = () => {
           Examples
         </Link>
 
+        <a
+          href="https://github.com/davidmonterocrespo24/velxio"
+          target="_blank"
+          rel="noopener noreferrer"
+          title="GitHub — Velxio"
+          style={{ display: 'flex', alignItems: 'center', gap: 5, color: '#ccc', textDecoration: 'none', fontSize: 13 }}
+        >
+          <svg width="16" height="16" viewBox="0 0 24 24" fill="currentColor">
+            <path d="M12 2C6.477 2 2 6.484 2 12.021c0 4.428 2.865 8.185 6.839 9.504.5.092.682-.217.682-.482 0-.237-.009-.868-.013-1.703-2.782.605-3.369-1.342-3.369-1.342-.454-1.154-1.11-1.462-1.11-1.462-.908-.62.069-.608.069-.608 1.003.07 1.531 1.032 1.531 1.032.892 1.53 2.341 1.088 2.91.832.092-.647.35-1.088.636-1.338-2.22-.253-4.555-1.113-4.555-4.951 0-1.093.39-1.988 1.029-2.688-.103-.253-.446-1.272.098-2.65 0 0 .84-.27 2.75 1.026A9.564 9.564 0 0 1 12 6.844a9.59 9.59 0 0 1 2.504.337c1.909-1.296 2.747-1.026 2.747-1.026.546 1.378.202 2.397.1 2.65.64.7 1.028 1.595 1.028 2.688 0 3.848-2.338 4.695-4.566 4.944.359.309.678.919.678 1.852 0 1.336-.012 2.415-.012 2.743 0 .267.18.578.688.48C19.138 20.203 22 16.447 22 12.021 22 6.484 17.523 2 12 2z" />
+          </svg>
+          GitHub
+        </a>
+
         {/* Auth UI */}
         {user ? (
           <div style={{ position: 'relative' }} ref={dropdownRef}>