feat: 完善审批退回流程与报销申请关联

后端优化报销单访问策略和常量定义，增强退回原因和审批状态
流转，前端完善退回对话框和审批交互组件，新增报销申请关联
模型，优化文档中心行数据和审批收件箱工具函数，增强引导
流程和会话模型，补充单元测试覆盖。

web/tests/expense-application-fast-preview.test.mjs

@@ -17,6 +17,10 @@ import {
   shouldUseLocalApplicationPreview
 } from '../src/utils/expenseApplicationPreview.js'
 import { renderMarkdown } from '../src/utils/markdown.js'
+import {
+  createMessage as createConversationMessage,
+  hasMeaningfulSessionMessages
+} from '../src/views/scripts/travelReimbursementConversationModel.js'
 
 const submitComposerScript = readFileSync(
   fileURLToPath(new URL('../src/views/scripts/useTravelReimbursementSubmitComposer.js', import.meta.url)),
@@ -217,6 +221,23 @@ test('application quick start renders a template without model review', () => {
   assert.match(buildApplicationPreviewFooterMessage(preview), /当前还需要补充/)
 })
 
+test('application quick start template counts as deletable session content', () => {
+  const welcomeMessage = createConversationMessage('assistant', '欢迎语', [], {
+    isWelcome: true,
+    welcomeQuickActions: [{ label: '快速发起申请', action: 'start_guided_application' }]
+  })
+  const templateMessage = createConversationMessage('assistant', '申请模板', [], {
+    applicationPreview: buildApplicationTemplatePreview({
+      name: '测试员工',
+      departmentName: '财务部',
+      grade: 'P5'
+    })
+  })
+
+  assert.equal(hasMeaningfulSessionMessages([welcomeMessage]), false)
+  assert.equal(hasMeaningfulSessionMessages([welcomeMessage, templateMessage]), true)
+})
+
 test('application session shows intent flow, persists preview, and supports inline table edit', () => {
   assert.match(submitComposerScript, /shouldUseLocalApplicationPreview/)
   assert.match(submitComposerScript, /buildLocalApplicationPreviewMessage/)
@@ -228,7 +249,7 @@ test('application session shows intent flow, persists preview, and supports inli
   assert.match(submitComposerScript, /startFlowStep\('intent'/)
   assert.match(submitComposerScript, /startFlowStep\('application-review-preview'/)
   assert.match(submitComposerScript, /completeFlowStep\('intent'/)
-  assert.match(submitComposerScript, /insightPanelCollapsed\.value = true/)
+  assert.doesNotMatch(submitComposerScript, /insightPanelCollapsed\.value = true/)
   assert.doesNotMatch(submitComposerScript, /void refineApplicationPreviewWithModel/)
   assert.match(submitComposerScript, /return null[\s\S]*const hasUnsavedReviewDraft/)
   assert.ok(
@@ -239,7 +260,7 @@ test('application session shows intent flow, persists preview, and supports inli
   assert.match(createViewScript, /const isApplicationSession = computed/)
   assert.match(createViewScript, /insightPanelCollapsed,/)
   assert.doesNotMatch(createViewScript, /if \(isApplicationSession\.value\) \{\s*return false\s*\}/)
-  assert.match(createViewScript, /flowSteps\.value\.length > 0/)
+  assert.match(createViewScript, /activeFlowSteps\.value\.length > 0/)
   assert.match(createViewScript, /useApplicationPreviewEditor/)
   assert.match(createViewScript, /message-bubble-application-preview/)
   assert.match(createViewScript, /buildApplicationPreviewFooterMessage/)
@@ -248,6 +269,8 @@ test('application session shows intent flow, persists preview, and supports inli
   assert.match(createViewScript, /user_input_text: applicationSubmitText/)
   assert.match(conversationModelScript, /applicationPreview: null/)
   assert.match(conversationModelScript, /applicationPreview: message\.applicationPreview \|\| null/)
+  assert.match(conversationModelScript, /\|\| message\.applicationPreview/)
+  assert.match(createViewScript, /hasMeaningfulSessionMessages\(messages\.value\)/)
 
   assert.match(messageItemTemplate, /class="application-preview-table"/)
   assert.match(messageItemTemplate, /class="application-preview-footer application-preview-footer-missing"/)