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_user_access_level.go

@@ -0,0 +1,27 @@
+package flow
+
+import "github.com/gogf/gf/v2/util/gconv"
+
+var (
+	FlowUserAccessLevelPrivate = newFlowUserAccessLevel(gconv.PtrInt8(1), "private")
+	FlowUserAccessLevelTeam    = newFlowUserAccessLevel(gconv.PtrInt8(2), "team")
+	FlowUserAccessLevelPublic  = newFlowUserAccessLevel(gconv.PtrInt8(3), "public")
+)
+
+type FlowUserAccessLevel *int8
+
+type flowUserAccessLevel struct {
+	code FlowUserAccessLevel
+	desc string
+}
+
+func (s flowUserAccessLevel) Code() FlowUserAccessLevel {
+	return s.code
+}
+func (s flowUserAccessLevel) Desc() string {
+	return s.desc
+}
+
+func newFlowUserAccessLevel(code FlowUserAccessLevel, desc string) flowUserAccessLevel {
+	return flowUserAccessLevel{code: code, desc: desc}
+}