refactor platform logic and add gasorder domain

backend/api/internal/models/gasorder_status.go

@@ -0,0 +1,22 @@
+package models
+
+import (
+	"time"
+
+	"git.apinb.com/bsm-sdk/core/database"
+)
+
+// GasorderStatus 对应 gasorder_status，保存不可变订单状态历史。
+type GasorderStatus struct {
+	Entity                     // 公共实体字段
+	GasorderBasicID  uint64    `gorm:"column:gasorder_basic_id;not null;index" json:"gasorder_basic_id"`                       // 订单自增主键
+	FromStatus       string    `gorm:"column:from_status;type:varchar(32);not null;default:''" json:"from_status"`             // 原状态
+	ToStatus         string    `gorm:"column:to_status;type:varchar(32);not null;index" json:"to_status"`                      // 新状态
+	OperatorIdentity string    `gorm:"column:operator_identity;type:varchar(36);not null;default:''" json:"operator_identity"` // 操作人标识
+	OperatorName     string    `gorm:"column:operator_name;type:varchar(64);not null;default:''" json:"operator_name"`         // 操作人姓名快照
+	OccurredAt       time.Time `gorm:"column:occurred_at;type:timestamptz;not null;index" json:"occurred_at"`                  // 发生时间
+	Reason           string    `gorm:"column:reason;type:text;not null;default:''" json:"reason"`                              // 变更原因
+}
+
+func init()                                     { database.AppendMigrate(&GasorderStatus{}) }
+func (table *GasorderStatus) TableName() string { return "gasorder_status" }