feat: 增加差旅报销标准测算和财务终审流程

新增差旅报销测算接口及 Spreadsheet 规则解析，审批流程拆分
直属领导审批与财务终审两阶段并细分权限，修复 PDF 文本层
缺失时自动回退 OCR，提交后清理关联会话，前端适配审批流
交互并补充单元测试。

web/src/views/TravelRequestDetailView.vue

@@ -375,15 +375,15 @@
             </article>
 
             <article v-if="showLeaderApprovalPanel" class="detail-card panel leader-approval-card">
-              <h3>领导意见</h3>
+              <h3>{{ approvalOpinionTitle }}</h3>
               <textarea
                 v-model="leaderOpinion"
                 maxlength="500"
-                placeholder="请输入审批意见，可补充核实情况、费用合理性或后续财务关注点。"
-                aria-label="领导意见"
+                :placeholder="approvalOpinionPlaceholder"
+                :aria-label="approvalOpinionTitle"
               ></textarea>
               <div class="leader-opinion-meta">
-                <span>审批通过后将流转至财务审批。</span>
+                <span>{{ approvalOpinionHint }}</span>
                 <strong>{{ leaderOpinion.length }}/500</strong>
               </div>
             </article>
@@ -620,10 +620,10 @@
 
     <ConfirmDialog
       :open="approveConfirmDialogOpen"
-      badge="领导审批"
+      :badge="approvalConfirmBadge"
       badge-tone="info"
       :title="`确认通过 ${request.id} 吗？`"
-      description="确认后该报销单会从直属领导审批流转到财务审批，请确认申请信息与领导意见无误。"
+      :description="approvalConfirmDescription"
       cancel-text="返回核对"
       confirm-text="确认通过"
       busy-text="通过中..."
@@ -644,10 +644,10 @@
         </div>
         <div class="submit-confirm-row">
           <span>下一节点</span>
-          <strong>财务审批</strong>
+          <strong>{{ approvalNextStage }}</strong>
         </div>
         <div class="submit-confirm-row">
-          <span>领导意见</span>
+          <span>{{ approvalOpinionTitle }}</span>
           <strong>{{ leaderOpinion.trim() || '未填写' }}</strong>
         </div>
       </div>