fix: ShippingController extends WP_REST_Controller

Fixed fatal error in ShippingController.

Issue:
- ShippingController extended BaseController (does not exist)
- Caused PHP fatal error: Class not found

Fix:
- Changed to extend WP_REST_Controller (WordPress standard)
- Matches pattern used by PaymentsController and StoreController
- Added proper PHPDoc header

Result:
✅ API endpoint now works
✅ No more 500 errors
✅ Shipping zones load correctly

includes/Api/ShippingController.php

@@ -1,11 +1,20 @@
 <?php
+/**
+ * Shipping REST API Controller
+ * 
+ * Provides REST endpoints for shipping zones and methods management.
+ * 
+ * @package WooNooW
+ */
+
 namespace WooNooW\Api;
 
+use WP_REST_Controller;
 use WP_REST_Request;
 use WP_REST_Response;
 use WC_Shipping_Zones;
 
-class ShippingController extends BaseController {
+class ShippingController extends WP_REST_Controller {
 
 	protected $namespace = 'woonoow/v1';
 	protected $rest_base = 'settings/shipping';