fix: remove extra header in mobile nav

ui/src/components/ui/NavBar.vue

@@ -79,7 +79,7 @@ const handleLinkClick = () => {
     <!-- encabezado dentro de sidebar -->
     <div class="flex items-center justify-between px-4 py-4 md:px-5 md:py-4 md:border-none"
          style="border-bottom-color: var(--secondary-color); border-bottom-width: 1px;">
-      <span class="text-lg font-semibold md:hidden" style="color: var(--primary-color);">Núcleo</span>
+      <!-- Intentionally left empty to preserve spacing on mobile -->
     </div>
 
     <!-- navegación -->