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/approval-center-detail-reuse.test.mjs

@@ -0,0 +1,39 @@
+import assert from 'node:assert/strict'
+import { readFileSync } from 'node:fs'
+import test from 'node:test'
+import { fileURLToPath } from 'node:url'
+
+const approvalTemplate = readFileSync(
+  fileURLToPath(new URL('../src/views/ApprovalCenterView.vue', import.meta.url)),
+  'utf8'
+)
+const approvalScript = readFileSync(
+  fileURLToPath(new URL('../src/views/scripts/ApprovalCenterView.js', import.meta.url)),
+  'utf8'
+)
+const detailTemplate = readFileSync(
+  fileURLToPath(new URL('../src/views/TravelRequestDetailView.vue', import.meta.url)),
+  'utf8'
+)
+const detailScript = readFileSync(
+  fileURLToPath(new URL('../src/views/scripts/TravelRequestDetailView.js', import.meta.url)),
+  'utf8'
+)
+
+test('approval center reuses reimbursement detail view instead of its old detail shell', () => {
+  assert.match(approvalTemplate, /<TravelRequestDetailView/)
+  assert.match(approvalTemplate, /back-label="返回审批列表"/)
+  assert.match(approvalTemplate, /approval-mode/)
+  assert.doesNotMatch(approvalTemplate, /class="approval-detail"/)
+  assert.doesNotMatch(approvalTemplate, /<ReturnReasonDialog/)
+  assert.doesNotMatch(approvalTemplate, /<ConfirmDialog/)
+
+  assert.match(approvalScript, /import TravelRequestDetailView from '\.\.\/TravelRequestDetailView\.vue'/)
+  assert.match(approvalScript, /fetchApprovalExpenseClaims/)
+  assert.doesNotMatch(approvalScript, /fetchExpenseClaims/)
+  assert.doesNotMatch(approvalScript, /import ConfirmDialog/)
+  assert.doesNotMatch(approvalScript, /import ReturnReasonDialog/)
+
+  assert.match(detailScript, /backLabel:/)
+  assert.match(detailTemplate, /\{\{ backLabel \}\}/)
+})