Use AdminMenu component in header

- Import and use existing AdminMenu component instead of simple link
- Displays dropdown menu with all admin section links when clicked
- Includes logout button in admin menu

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/components/Header.tsx

@@ -9,6 +9,7 @@ import MobileNav from './MobileNav';
 import { prisma } from '@/lib/prisma';
 import { getCurrentCustomer } from '@/lib/auth';
 import { isAdminAuthenticated } from '@/lib/adminAuth';
+import AdminMenu from './AdminMenu';
 
 export default async function Header() {
   const [categories, collections, customer, isAdmin] = await Promise.all([
@@ -71,11 +72,7 @@ export default async function Header() {
         </nav>
         <div className="flex items-center gap-2 sm:gap-4">
           <CurrencySelector />
-          {isAdmin && (
-            <Link href="/admin/orders" className="tag-label hover:text-ink">
-              Admin
-            </Link>
-          )}
+          {isAdmin && <AdminMenu />}
           <div className="hidden md:block">
             <AccountMenu customer={customer ? { name: customer.name, email: customer.email } : null} />
           </div>