feat: add customer login page in SPA

- Created Login/index.tsx with styled form
- Added /auth/customer-login API endpoint (no admin perms required)
- Registered route in Routes.php
- Added /login route in customer-spa App.tsx
- Account page now redirects to SPA login instead of wp-login.php
- Login supports redirect param for post-login navigation

includes/Api/Routes.php

@@ -65,6 +65,13 @@ class Routes {
                 'permission_callback' => '__return_true',
             ] );
             
+            // Customer login endpoint (no admin permission required)
+            register_rest_route( $namespace, '/auth/customer-login', [
+                'methods'             => 'POST',
+                'callback'            => [ AuthController::class, 'customer_login' ],
+                'permission_callback' => '__return_true',
+            ] );
+            
             // Defer to controllers to register their endpoints
             CheckoutController::register();
             OrdersController::register();