fix: mobile responsive admin panel

frontend/admin/admin.js

@@ -13,6 +13,18 @@
     const createForm = document.getElementById('create-form');
     const createAlert = document.getElementById('create-alert');
     const btnLogout = document.getElementById('btn-logout');
+    const menuToggle = document.getElementById('menu-toggle');
+    const sidebar = document.querySelector('.sidebar');
+    const sidebarOverlay = document.getElementById('sidebar-overlay');
+
+    // ---- Mobile Menu ----
+    function toggleSidebar() {
+        sidebar.classList.toggle('open');
+        sidebarOverlay.classList.toggle('open');
+    }
+
+    menuToggle.addEventListener('click', toggleSidebar);
+    sidebarOverlay.addEventListener('click', toggleSidebar);
 
     const ROLE_LABELS = {
         ADMIN: 'Администратор',