feat(erp): 添加应收账款业务日期字段

- 在ReplyReceivableInfo结构体中新增businessDate字段
- 该字段用于记录应收账款的业务发生日期
- 字段类型为*time.Time指针类型，支持空值处理
- JSON序列化名称为businessDate，保持与前端约定一致

erp/receivable.go

@@ -72,6 +72,7 @@ func (r *receivable) Gen(ctx context.Context, shipmentId int64) (err error) {
 type ReplyReceivableInfo struct {
 	Id                   int64                          `json:"id"`
 	ReceivableSerial     string                         `json:"receivableSerial"`
+	BusinessDate         *time.Time                     `json:"businessDate"`
 	CustomName           string                         `json:"customName"`
 	InvoiceSerial        string                         `json:"invoiceSerial"`
 	ReceivableAmount     decimal.Decimal                `json:"receivableAmount"`