Add customer login activity logging

- Add CustomerLoginLog model to track customer login attempts
- Record successful and failed customer logins
- Capture email, IP address, and user agent for each attempt
- Create /admin/customer-login-logs page to view activity
- Show login stats (successes, failures, active customers)
- Display browser/device and IP for each login attempt
- Add "Customer login activity" link to admin menu
- Monitor customer access patterns and detect suspicious activity
- Last 30 days active customer count

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

src/components/AdminMenu.tsx

@@ -22,7 +22,8 @@ const ADMIN_LINKS = [
   { href: '/admin/collections', label: 'All collections' },
   { href: '/admin/customers', label: 'Email customers' },
   { href: '/admin/maintenance', label: 'Maintenance' },
-  { href: '/admin/login-logs', label: 'Login activity' },
+  { href: '/admin/login-logs', label: 'Admin login activity' },
+  { href: '/admin/customer-login-logs', label: 'Customer login activity' },
 ];
 
 export default function AdminMenu() {