feat(backoffice): Backoffice for Hackathon - user management page (#67)

* feat(backoffice): create a boilerplate page for Hackathon dashboard

- Create an empty page for Hackathon dashboard
- Comment out and hide the existing backoffice sidebar

* feat(backoffice): Create a nested/dropdown sidebar list

- Create a dropdown sidebar list
- Show back the old navigation and group them
- Make the sidebar responsive for mobile view

* test datatable with mock data

* base UI for Hackathon backoffice

TODO:
- Organize table schema for users, teams, and submissions management
- Create API Contract for additional back-end endpoint

* feat(hackathon): draft data table column & API Contract

* update endpoint

* feat(backoffice): update page hackathon user management

- update data table component
- update filtering & pagination
- add modal display to edit and add user
- hide notification icon in backoffice wrapper

* feat(backoffice): add API contract for hackathon users

* feat(backoffice): little adjustment in hackathon users management UI and API contract

apps/backoffice/src/app/(protected)/layout.tsx

@@ -1,13 +1,51 @@
-import { FC, ReactElement } from 'react';
+import { FC, ReactElement, useState } from 'react';
 import { Outlet } from 'react-router-dom';
 import { BackofficeSidebar } from '@imphnen-frontend-service/ui/organisms';
 
 export const AppLayout: FC = (): ReactElement => {
+  const [mobileSidebarOpen, setMobileSidebarOpen] = useState(false);
+
   return (
     <div className="bg-primary-50 min-h-screen flex justify-center">
       <div className="bg-primary-50 min-h-screen w-full flex">
-        <BackofficeSidebar />
+        <BackofficeSidebar
+          isOpen={mobileSidebarOpen}
+          onClose={() => setMobileSidebarOpen(false)}
+        />
         <div className="flex-1 overflow-auto">
+          {/* Sticky top header */}
+          <header
+            className={
+              'lg:hidden sticky top-0 bg-white border-b border-primary-200 px-4 py-3 flex items-center gap-3 ' +
+              (mobileSidebarOpen ? 'z-0' : 'z-30')
+            }
+          >
+            {/* Mobile menu button (shown on small screens) */}
+            <button
+              type="button"
+              className="lg:hidden p-2 rounded-md hover:bg-gray-100 text-gray-700"
+              onClick={() => setMobileSidebarOpen(true)}
+              aria-label="Open sidebar"
+            >
+              <svg
+                className="w-5 h-5"
+                fill="none"
+                stroke="currentColor"
+                viewBox="0 0 24 24"
+              >
+                <path
+                  strokeLinecap="round"
+                  strokeLinejoin="round"
+                  strokeWidth={2}
+                  d="M4 6h16M4 12h16M4 18h16"
+                />
+              </svg>
+            </button>
+            <h1 className="text-p3 font-semibold text-primary-700">
+              IMPHNEN Backoffice
+            </h1>
+          </header>
+
           <Outlet />
         </div>
       </div>