UX: Add Dashboard link to admin menu on main site

- Admin users now see "Admin" dropdown in header when on main site
- Dashboard link added as first item in admin menu
- Quick access to admin panel from any page on main site
- Allows admins to navigate between site and admin panel easily

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

src/components/AdminMenu.tsx

@@ -11,7 +11,8 @@ interface MenuItem {
 }
 
 const ADMIN_LINKS: MenuItem[] = [
-  { href: '/admin/orders', label: 'Orders' },
+  { href: '/admin/dashboard', label: '📊 Dashboard' },
+  { href: '/admin/orders', label: '📦 Orders' },
   {
     label: '💰 Financial',
     submenu: [