feat: 细化差旅票据费用明细分类并自动计算出差补贴

将差旅费用明细拆分为火车票、机票、住宿票、乘车等细分类
型，根据票据字段自动生成行程/事由描述，结合规则引擎自
动计算出差补贴金额，前端适配费用明细编辑和差旅票据审
核交互，补充单元测试覆盖。

server/src/app/api/v1/endpoints/reimbursements.py

@@ -18,6 +18,7 @@ from app.schemas.reimbursement import (
     ExpenseClaimItemUpdate,
     ExpenseClaimRead,
     ExpenseClaimReturnPayload,
+    ExpenseClaimUpdate,
     ReimbursementCreate,
     ReimbursementRead,
     TravelReimbursementCalculatorRequest,
@@ -115,6 +116,43 @@ def get_expense_claim(claim_id: str, db: DbSession, current_user: CurrentUser) -
     return claim
 
 
+@router.patch(
+    "/claims/{claim_id}",
+    response_model=ExpenseClaimRead,
+    summary="更新草稿报销单",
+    description="更新草稿待提交报销单的主说明等草稿字段。",
+    responses={
+        status.HTTP_404_NOT_FOUND: {
+            "model": ErrorResponse,
+            "description": "报销单不存在。",
+        },
+        status.HTTP_400_BAD_REQUEST: {
+            "model": ErrorResponse,
+            "description": "报销单状态不允许更新。",
+        },
+    },
+)
+def update_expense_claim(
+    claim_id: str,
+    payload: ExpenseClaimUpdate,
+    db: DbSession,
+    current_user: CurrentUser,
+) -> ExpenseClaimRead:
+    service = ExpenseClaimService(db)
+    try:
+        claim = service.update_claim(
+            claim_id=claim_id,
+            payload=payload,
+            current_user=current_user,
+        )
+    except ValueError as error:
+        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(error)) from error
+
+    if claim is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Claim not found")
+    return claim
+
+
 @router.patch(
     "/claims/{claim_id}/items/{item_id}",
     response_model=ExpenseClaimRead,