feat: Add AppHeader component and implement the default application layout.

Frontend-Learner/layouts/default.vue

@@ -5,11 +5,7 @@
  * Uses Quasar QLayout for responsive structure.
  */
 
-const leftDrawerOpen = ref(false)
 
-const toggleLeftDrawer = () => {
-  leftDrawerOpen.value = !leftDrawerOpen.value
-}
 
 // Initialize global theme management
 useThemeMode()
@@ -22,19 +18,9 @@ useThemeMode()
       bordered
       class="!bg-white dark:!bg-[#1e293b] !text-slate-900 dark:!text-white border-b border-slate-200 dark:border-slate-700"
     >
-      <AppHeader @toggle-sidebar="toggleLeftDrawer" />
+      <AppHeader />
     </q-header>
 
-    <!-- Sidebar (Drawer) -->
-    <q-drawer
-      v-model="leftDrawerOpen"
-      bordered
-      class="!bg-white dark:!bg-[#1e293b] !text-slate-900 dark:!text-white border-r border-slate-200 dark:border-slate-700"
-      :width="260"
-    >
-      <AppSidebar />
-    </q-drawer>
-
     <!-- Main Content -->
     <q-page-container>
       <q-page class="relative">