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/tests/test_knowledge_rag_service.py

@@ -238,7 +238,7 @@ def test_resolve_default_qdrant_url_falls_back_to_loopback(monkeypatch) -> None:
     assert knowledge_rag_module._resolve_default_qdrant_url() == "http://127.0.0.1:6333"
 
 
-def test_runtime_cache_is_isolated_by_thread(monkeypatch) -> None:
+def test_runtime_cache_uses_dedicated_instance_across_calling_threads(monkeypatch) -> None:
     knowledge_rag_module.shutdown_knowledge_rag_runtime()
     created_runtimes = []
 
@@ -270,8 +270,8 @@ def test_runtime_cache_is_isolated_by_thread(monkeypatch) -> None:
     thread.start()
     thread.join(timeout=5)
 
-    assert len(created_runtimes) == 2
-    assert worker_runtimes[0] is not main_runtime
+    assert len(created_runtimes) == 1
+    assert worker_runtimes[0] is main_runtime
 
     knowledge_rag_module.shutdown_knowledge_rag_runtime()
     assert all(runtime.finalized for runtime in created_runtimes)