Refactor: Update Navbar and TopBar UI

This commit implements the following changes:

1. Removed the close button (✕) from within the NavBar component (`ui/src/components/ui/NavBar.vue`). The sidebar is now exclusively controlled by the hamburger icon in the TopBar.
2. Moved the hamburger menu button in the TopBar component (`ui/src/components/ui/TopBar.vue`) to the left side of the application title ("Núcleo").
3. Improved the visual styling of the hamburger button in `TopBar.vue` with increased padding, consistent border-radius, and clearer hover and focus states for better usability and accessibility.

These changes address the issue of redundant close buttons and aim to provide a cleaner and more intuitive navigation experience.

ui/src/components/ui/NavBar.vue

@@ -80,10 +80,6 @@ const handleLinkClick = () => {
     <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>
-      <button class="close-btn h-8 w-8 flex items-center justify-center rounded-full border transition duration-200"
-              @click="ui.toggleSidebar">
-        ✕
-      </button>
     </div>
 
     <!-- navegación -->

ui/src/components/ui/TopBar.vue

@@ -7,26 +7,39 @@ const ui = useUi()
   <!-- barra superior fija -->
   <header class="fixed top-0 left-0 right-0 h-14 flex items-center justify-between px-4 md:px-6 z-50 shadow-sm"
           :style="{ backgroundColor: 'var(--background-color)', borderBottom: '1px solid var(--secondary-color)' }">
-    <!-- título -->
-    <h1 class="text-lg font-semibold tracking-wide select-none" :style="{ color: 'var(--primary-color)' }">Núcleo</h1>
-
     <!-- botón hamburguesa (visible solo en mobile) -->
     <button
       @click="ui.toggleSidebar"
       class="hamburger-button inline-flex items-center justify-center h-9 w-9 rounded-md text-white transition">
       &#9776;
     </button>
+
+    <!-- título -->
+    <h1 class="text-lg font-semibold tracking-wide select-none" :style="{ color: 'var(--primary-color)' }">Núcleo</h1>
   </header>
 </template>
 
 <style scoped>
 .hamburger-button {
   background-color: var(--primary-color);
+  color: white; /* Assuming primary-color is dark enough for white text */
+  padding: 0.5rem; /* Increased padding */
+  border-radius: 0.375rem; /* Consistent border radius */
+  transition: background-color 0.2s ease-in-out, filter 0.2s ease-in-out;
+  line-height: 1; /* Ensure icon is centered if it's text-based */
 }
+
 .hamburger-button:hover {
-  filter: brightness(1.1); /* Slight lighten/darken based on primary color */
+  filter: brightness(1.15); /* Slightly more noticeable hover brightness */
+}
+
+.hamburger-button:focus {
+  outline: 2px solid var(--primary-color); /* Simple outline for focus */
+  outline-offset: 2px; /* Offset outline slightly */
+}
+
+.hamburger-button:focus-visible { /* More modern focus indication */
+  outline: 2px solid var(--primary-color);
+  outline-offset: 2px;
 }
-/* Alternative hover if primary is very light or very dark, requiring specific color adjustment */
-/* .hamburger-button:hover { background-color: var(--primary-color-hover); } */
-/* Ensure --primary-color-hover is defined or calculated based on --primary-color if this approach is used */
 </style>