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。

server/tests/test_document_intelligence.py

@@ -51,6 +51,27 @@ def test_document_intelligence_extracts_larger_decimal_amount_from_multiple_cand
     assert any(field.label == "金额" and field.value == "13.4元" for field in insight.fields)
 
 
+def test_document_intelligence_prefers_train_ticket_for_railway_e_ticket_invoice_text() -> None:
+    insight = build_document_insight(
+        filename="铁路电子客票.pdf",
+        summary="电子发票（铁路电子客票）",
+        text=(
+            "电子发票（铁路电子客票）\n"
+            "发票号码:26319166100006175398\n"
+            "上海虹桥站\n"
+            "武汉站\n"
+            "G456\n"
+            "二等座\n"
+            "票价:￥354.00"
+        ),
+    )
+
+    assert insight.document_type == "train_ticket"
+    assert insight.document_type_label == "火车/高铁票"
+    assert insight.scene_code == "travel"
+    assert any(field.label == "金额" and field.value == "354元" for field in insight.fields)
+
+
 def test_document_intelligence_service_keeps_rule_fields_without_model_correction() -> None:
     engine = create_engine(
         "sqlite+pysqlite:///:memory:",