fix: remove unused CancelOrderRequest struct

model/order.go

@@ -31,8 +31,6 @@ type AcceptOrderRequest struct {
 	ProviderID string `json:"provider_id" binding:"required"`
 }
 
-type CancelOrderRequest struct{}
-
 type AppError struct {
 	Code       string `json:"error"`
 	Message    string `json:"message"`