feat: Enhance mobile sidebar with sticky header and search functionality

Author: denisdobra10

docs-v3/.data/content/contents.sqlite

@@ -13,7 +13,7 @@
         @click.stop
         @touchmove.stop
       >
-        <div class="flex items-center justify-between px-4 py-4 border-b border-gray-200 dark:border-gray-700 flex-shrink-0">
+        <div class="sticky top-0 z-10 flex items-center justify-between px-4 py-4 border-b border-gray-200 dark:border-gray-700 flex-shrink-0 bg-white dark:bg-gray-900">
           <h2 class="text-lg font-semibold text-gray-900 dark:text-white">{{ title }}</h2>
           <button
             @click.stop="$emit('close')"

docs-v3/components/MobileSidebarOverlay.vue

@@ -20,6 +20,11 @@
     title="Documentation"
     @close="toggleMobileMenu"
   >
+    <!-- Mobile Search -->
+    <div class="mb-6">
+      <UContentSearchButton label="Search docs..." :collapsed="false" class="w-full" @click="toggleMobileMenu" />
+    </div>
+    
     <div class="space-y-6">
       <NavigationSection 
         v-for="section in navigationSections"