feat: 新增预算费控模型与报销审批流引擎

后端新增预算费控服务和报销单审批流模块，引入申请人费用画像
算法，优化知识库 RAG 运行时和同步逻辑，完善报销单工作流常
量和明细同步，更新差旅报销规则电子表格，前端新增预算分析
组件和数字员工模型，完善审批对话框和洞察面板交互，优化侧
边栏和顶栏样式，补充单元测试。

server/src/app/services/expense_claim_read_model.py

@@ -204,6 +204,8 @@ class ExpenseClaimReadModelMixin:
         normalized = str(stage or "").strip()
         if "直属" in normalized or "领导" in normalized or "负责人" in normalized:
             return "direct_manager"
+        if "预算" in normalized:
+            return "budget"
         if "财务" in normalized:
             return "finance"
         if "AI" in normalized or "预审" in normalized: