feat: 完善报销单审批流程及退回原因追踪

新增直属领导审批通过接口和审批待办列表查询，报销单退回
支持原因码分类和审批环节标记，优化票据附件去重和路径
回退查找，前端新增退回原因对话框、审批收件箱和工作台
图标组件，补充工具函数和单元测试覆盖。

web/tests/accessControl.test.mjs

@@ -0,0 +1,21 @@
+import assert from 'node:assert/strict'
+import test from 'node:test'
+
+import { canManageExpenseClaims, canReturnExpenseClaims } from '../src/utils/accessControl.js'
+
+test('direct approvers can return claims without receiving delete permissions', () => {
+  const managerUser = { roleCodes: ['manager'] }
+  const approverUser = { roleCodes: ['approver'] }
+
+  assert.equal(canReturnExpenseClaims(managerUser), true)
+  assert.equal(canReturnExpenseClaims(approverUser), true)
+  assert.equal(canManageExpenseClaims(managerUser), false)
+  assert.equal(canManageExpenseClaims(approverUser), false)
+})
+
+test('finance and executives can return and manage claims', () => {
+  assert.equal(canReturnExpenseClaims({ roleCodes: ['finance'] }), true)
+  assert.equal(canManageExpenseClaims({ roleCodes: ['finance'] }), true)
+  assert.equal(canReturnExpenseClaims({ roleCodes: ['executive'] }), true)
+  assert.equal(canManageExpenseClaims({ roleCodes: ['executive'] }), true)
+})