fix: persist the canceled order returned by cancel() in OrderService

Author: otaviojava

src/main/java/org/soujava/samples/ai/patterns/planning/OrderService.java

@@ -33,10 +33,7 @@ public String getActiveOrderNumber(String customerId) {
     public String cancelOrder(String orderNumber) {
         LOGGER.info("[TOOL EXECUTION] Calling payment gateway to cancel: " + orderNumber);
         Optional<Order> order = repository.findById(UUID.fromString(orderNumber));
-        order.ifPresent(o -> {
-            o.cancel();
-            repository.save(o);
-        });
+        order.ifPresent(o -> repository.save(o.cancel()));
         return order.isPresent() ? "SUCCESS - $45.00 Refunded" : "ORDER_NOT_FOUND";
     }
 }