feat(flows): 新增流程编辑器基础功能与相关组件

feat(backend): 添加流程模型与服务支持
feat(frontend): 实现流程编辑器UI与交互
feat(assets): 添加流程节点图标资源
feat(plugins): 实现上下文菜单和运行时插件
feat(components): 新增基础节点和侧边栏组件
feat(routes): 添加流程相关路由配置
feat(models): 创建流程和运行日志数据模型
feat(services): 实现流程服务层逻辑
feat(migration): 添加流程相关数据库迁移
feat(config): 更新前端配置支持流程编辑器
feat(utils): 增强axios错误处理和工具函数

backend/src/flow/domain.rs

@@ -0,0 +1,44 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, Hash, Default)]
+pub struct NodeId(pub String);
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum NodeKind {
+    Start,
+    End,
+    Task,
+    Decision,
+}
+
+impl Default for NodeKind {
+    fn default() -> Self { Self::Task }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct NodeDef {
+    pub id: NodeId,
+    #[serde(default)]
+    pub kind: NodeKind,
+    #[serde(default)]
+    pub name: String,
+    #[serde(default)]
+    pub task: Option<String>, // 绑定的任务组件标识
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct LinkDef {
+    pub from: NodeId,
+    pub to: NodeId,
+    #[serde(default)]
+    pub condition: Option<String>, // 条件脚本，返回 bool
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct ChainDef {
+    #[serde(default)]
+    pub name: String,
+    pub nodes: Vec<NodeDef>,
+    #[serde(default)]
+    pub links: Vec<LinkDef>,
+}