fix(spec): include order number in webhook_service_spec expected data

The webhook_payload now includes :number in the order slice, but
webhook_service_spec still expected the order hash without it. Since
hash_including only matches at the top level, the nested order hash
comparison was strict and failed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

spec/services/payments/webhook_service_spec.rb

@@ -56,6 +56,7 @@ RSpec.describe Payments::WebhookService do
             }
           },
           order: {
+            number: order.number,
             total: order.total,
             currency: order.currency,
             line_items: line_items