Fix: Add Design Approvals and Shipping rates to admin dropdown menu

Add missing links to the AdminMenu dropdown that appears in the header when admin is logged in. These links now appear right after Orders for easy access.

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

src/components/AdminMenu.tsx

@@ -13,6 +13,8 @@ interface MenuItem {
 const ADMIN_LINKS: MenuItem[] = [
   { href: '/admin/dashboard', label: '📊 Dashboard' },
   { href: '/admin/orders', label: '📦 Orders' },
+  { href: '/admin/designs', label: '✓ Design Approvals' },
+  { href: '/admin/shipping-rates', label: '🚚 Shipping rates' },
   {
     label: '💰 Financial',
     submenu: [