fix: checkout improvements

1. Hidden fields now respected in SPA
   - Added isFieldHidden helper to check if PHP sets type to 'hidden'
   - Country/state/city fields conditionally rendered based on API response
   - Set default country value for hidden country fields (Indonesia-only stores)

2. Coupon discount now shows correct amount
   - Added calculate_totals() before reading discount
   - Changed coupons response to include {code, discount, type} per coupon
   - Added discount_total at root level for frontend compatibility

3. Order details page now shows shipping info and AWB tracking
   - Added shipping_lines, tracking_number, tracking_url to Order interface
   - Added Shipping Method section with courier name and cost
   - Added AWB tracking section for processing/completed orders
   - Track Shipment button with link to tracking URL

includes/Api/Controllers/CartController.php

@@ -131,6 +131,21 @@ class CartController extends WP_REST_Controller {
         
         $cart = WC()->cart;
         
+        // Calculate totals to ensure discounts are computed
+        $cart->calculate_totals();
+        
+        // Format coupons with discount amounts
+        $coupons_with_discounts = [];
+        foreach ($cart->get_applied_coupons() as $coupon_code) {
+            $coupon = new \WC_Coupon($coupon_code);
+            $discount = $cart->get_coupon_discount_amount($coupon_code);
+            $coupons_with_discounts[] = [
+                'code'     => $coupon_code,
+                'discount' => (float) $discount,
+                'type'     => $coupon->get_discount_type(),
+            ];
+        }
+        
         return new WP_REST_Response([
             'items'          => $this->format_cart_items($cart->get_cart()),
             'totals'         => [
@@ -145,7 +160,8 @@ class CartController extends WP_REST_Controller {
                 'total'          => $cart->get_total(''),
                 'total_tax'      => $cart->get_total_tax(),
             ],
-            'coupons'        => $cart->get_applied_coupons(),
+            'coupons'        => $coupons_with_discounts,
+            'discount_total' => (float) $cart->get_discount_total(), // Root level for frontend
             'needs_shipping' => $cart->needs_shipping(),
             'needs_payment'  => $cart->needs_payment(),
             'item_count'     => $cart->get_cart_contents_count(),