feat(server): 工作流扩展 leave 实体骨架（F24）

- workflow_instances 解耦 reimbursement FK：新增 reimbursement_id/leave_request_id + 回填迁移
- 新增 leave_requests 表与 /api/leave-requests 最小链路（create/submit）
- workflow approve/reject/return 支持 leave 状态更新；transfer 非报销任务禁用
- seed-config 增加 leave workflow definition；更新 v3 CSV 状态推进

server/src/scripts/seed-config.js

@@ -92,6 +92,19 @@ const DEFAULT_WORKFLOW_DEFINITION = {
   ],
 };
 
+const DEFAULT_LEAVE_WORKFLOW_DEFINITION = {
+  steps: [
+    {
+      id: "leave_approval_manager",
+      name: "部门审批",
+      type: "approval",
+      assignee_rule: {
+        type: "department_manager",
+      },
+    },
+  ],
+};
+
 async function seedExpenseTypes(prisma) {
   const now = new Date();
   const allTypes = [
@@ -198,6 +211,38 @@ async function seedWorkflowDefinition(prisma) {
       created_by: null,
     },
   });
+
+  await prisma.workflowDefinition.updateMany({
+    where: {
+      entity_type: "leave",
+    },
+    data: {
+      is_active: false,
+    },
+  });
+
+  await prisma.workflowDefinition.upsert({
+    where: {
+      entity_type_version: {
+        entity_type: "leave",
+        version: 1,
+      },
+    },
+    update: {
+      name: "请假审批流程(MVP)",
+      definition_json: DEFAULT_LEAVE_WORKFLOW_DEFINITION,
+      is_active: true,
+      created_by: null,
+    },
+    create: {
+      name: "请假审批流程(MVP)",
+      entity_type: "leave",
+      definition_json: DEFAULT_LEAVE_WORKFLOW_DEFINITION,
+      version: 1,
+      is_active: true,
+      created_by: null,
+    },
+  });
 }
 
 async function main() {
@@ -220,6 +265,8 @@ async function main() {
     console.log("- document sequence: reimbursement(reset_period=none)");
     // eslint-disable-next-line no-console
     console.log("- workflow definition: reimbursement v1 (1-step role=ceo)");
+    // eslint-disable-next-line no-console
+    console.log("- workflow definition: leave v1 (1-step department_manager)");
   } finally {
     await prisma.$disconnect();
     await pool.end();