feat: 新增工作流执行模块

新增流程执行记录的实体、DTO、DAO、控制器和服务层，支持工作流的执行、回调及结果树状列表查询；同时更新服务名称为 ai-agent。

workflow/consts/flow/flow_execution_status.go

@@ -0,0 +1,28 @@
+package flow
+
+import "github.com/gogf/gf/v2/util/gconv"
+
+var (
+	FlowExecutionStatusRunning = newFlowExecutionStatus(gconv.PtrInt8(1), "running") // 运行中
+	FlowExecutionStatusSuccess = newFlowExecutionStatus(gconv.PtrInt8(2), "success") // 成功
+	FlowExecutionStatusFailed  = newFlowExecutionStatus(gconv.PtrInt8(3), "failed")  // 失败
+	FlowExecutionStatusPaused  = newFlowExecutionStatus(gconv.PtrInt8(4), "paused")  // 暂停
+)
+
+type FlowExecutionStatus *int8
+
+type flowExecutionStatus struct {
+	code FlowExecutionStatus
+	desc string
+}
+
+func (s flowExecutionStatus) Code() FlowExecutionStatus {
+	return s.code
+}
+func (s flowExecutionStatus) Desc() string {
+	return s.desc
+}
+
+func newFlowExecutionStatus(code FlowExecutionStatus, desc string) flowExecutionStatus {
+	return flowExecutionStatus{code: code, desc: desc}
+}