feat(调度任务): 实现调度任务管理功能

新增调度任务模块，支持任务的增删改查、启停及手动执行
- 后端添加 schedule_job 模型、服务、路由及调度器工具类
- 前端新增调度任务管理页面
- 修改 flow 相关接口将 id 类型从 String 改为 i64
- 添加 tokio-cron-scheduler 依赖实现定时任务调度
- 初始化时加载已启用任务并注册到调度器

backend/src/models/flow.rs

@@ -4,7 +4,7 @@ use sea_orm::entity::prelude::*;
 #[sea_orm(table_name = "flows")]
 pub struct Model {
     #[sea_orm(primary_key)]
-    pub id: String,
+    pub id: i64,
     pub name: Option<String>,
     pub yaml: Option<String>,
     pub design_json: Option<String>,

backend/src/models/flow_run_log.rs

@@ -5,7 +5,7 @@ use sea_orm::entity::prelude::*;
 pub struct Model {
     #[sea_orm(primary_key)]
     pub id: i64,
-    pub flow_id: String,
+    pub flow_id: i64,
     // 新增：流程编码（可空）
     pub flow_code: Option<String>,
     pub input: Option<String>,

backend/src/models/mod.rs

@@ -11,4 +11,5 @@ pub mod request_log;
 pub mod position;
 pub mod user_position;
 pub mod flow;
-pub mod flow_run_log;
+pub mod flow_run_log;
+pub mod schedule_job;

backend/src/models/schedule_job.rs

@@ -0,0 +1,19 @@
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel, serde::Serialize, serde::Deserialize)]
+#[sea_orm(table_name = "schedule_jobs")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub id: String,
+    pub name: String,
+    pub cron_expr: String,
+    pub enabled: bool,
+    pub flow_code: String,
+    pub created_at: DateTimeWithTimeZone,
+    pub updated_at: DateTimeWithTimeZone,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {}
+
+impl ActiveModelBehavior for ActiveModel {}