fix(business): 唯一键冲突重试改为审计上下文内循环，单条审计无递归

三处 create（业务/发货/回款）的 return _retry_create 是吞异常后正常
退出：外层审计把已回滚的首次尝试记成 success（假成功），重入整个
create_* 违反 audit_service「不支持嵌套」约定，且 _NO_RETRY 死常量
导致持续冲突时无界递归至 RecursionError。改为 audit 内 for 循环
（上限 _NO_RETRY），rollback 后重新锁行与取号，成功/最终失败各恰好
一条审计。新增集成用例锁定两条路径的日志增量。

Co-Authored-By: Claude Code <noreply@anthropic.com>

backend/app/services/shipment_service.py

@@ -56,6 +56,9 @@ from app.services.no_generator import next_no
 
 logger = logging.getLogger(__name__)
 
+# 编号唯一键冲突后的重试次数（模式同 business_service._NO_RETRY）
+_NO_RETRY = 1
+
 
 def _to_out(row: tuple[Shipment, str]) -> ShipmentOut:
     """(shipment, business_no) → 响应模型；金额出参 str。"""
@@ -117,9 +120,7 @@ def _build_item_rows(items: list[ShipmentItemIn]) -> list[ShipmentItem]:
 
 def _generate_no(session: Session) -> str:
     """生成发货单号（SH 前缀；MAX+FOR UPDATE 与 1062 兜底见 no_generator）。"""
-    return next_no(
-        session, model=Shipment, column_name="shipment_no", prefix=NO_PREFIX_SHIPMENT
-    )
+    return next_no(session, model=Shipment, column_name="shipment_no", prefix=NO_PREFIX_SHIPMENT)
 
 
 def _ensure_business_writable(session: Session, business_id: int, action: str) -> Business:
@@ -220,57 +221,54 @@ def create_shipment(
         ),
         meta=meta,
     ):
-        if business is None:
-            raise NotFoundError("业务不存在")
-        if business.status != BUSINESS_STATUS_ACTIVE:
-            raise BadRequestError("业务已完成或已终止，禁止新发货")
+        # 单号唯一键冲突的重试整体收在审计上下文内（模式同
+        # business_service.create_business）：rollback 释放旧锁，重试前重新
+        # 锁业务行与生成编号——成功/最终失败各只记一条审计，无递归
+        for attempt in range(_NO_RETRY + 1):
+            try:
+                if business is None:
+                    raise NotFoundError("业务不存在")
+                if business.status != BUSINESS_STATUS_ACTIVE:
+                    raise BadRequestError("业务已完成或已终止，禁止新发货")
 
-        try:
-            shipment = Shipment(
-                shipment_no=shipment_no,
-                business_id=payload.business_id,
-                ship_date=payload.ship_date,
-                freight_amount=_amount_or_zero(payload.freight_amount),
-                total_amount=Decimal("0"),
-                remark=payload.remark,
-            )
-            shipment_repository.create(session, shipment)
-            shipment_repository.replace_items(
-                session, shipment.id, _build_item_rows(payload.items)
-            )
-            total = shipment_repository.sum_item_amount(session, shipment.id)
-            shipment.total_amount = total if total is not None else Decimal("0")
-            _recalc_totals(session, business)
-            out = _to_out((shipment, business.business_no))
-            new_id = shipment.id
-            session.commit()
-        except IntegrityError as exc:
-            session.rollback()
-            if _is_duplicate_entry(exc):
-                # 单号撞唯一键的残余竞态：兜底重试一次（防无限重试掩盖死锁）
-                return _retry_create(session, payload, operator=operator, meta=meta)
-            raise
+                shipment = Shipment(
+                    shipment_no=shipment_no,
+                    business_id=payload.business_id,
+                    ship_date=payload.ship_date,
+                    freight_amount=_amount_or_zero(payload.freight_amount),
+                    total_amount=Decimal("0"),
+                    remark=payload.remark,
+                )
+                shipment_repository.create(session, shipment)
+                shipment_repository.replace_items(
+                    session, shipment.id, _build_item_rows(payload.items)
+                )
+                total = shipment_repository.sum_item_amount(session, shipment.id)
+                shipment.total_amount = total if total is not None else Decimal("0")
+                _recalc_totals(session, business)
+                out = _to_out((shipment, business.business_no))
+                new_id, new_no = shipment.id, shipment_no  # 固化：commit 后不碰 ORM
+                session.commit()
+                break
+            except IntegrityError as exc:
+                session.rollback()
+                if _is_duplicate_entry(exc) and attempt < _NO_RETRY:
+                    business = business_repository.get_by_id(
+                        session, payload.business_id, for_update=True
+                    )
+                    shipment_no = _generate_no(session)
+                    continue
+                raise
 
         logger.info(
             "新增发货单 | shipment_id=%s | no=%s | business_id=%s",
             new_id,
-            shipment_no,
+            new_no,
             payload.business_id,
         )
         return out
 
 
-def _retry_create(
-    session: Session,
-    payload: ShipmentCreateIn,
-    *,
-    operator: User,
-    meta: RequestMeta | None,
-) -> ShipmentOut:
-    """单号撞唯一键后的单次重试（重新锁行与生成编号，防死锁类缺陷掩盖）。"""
-    return create_shipment(session, payload, operator=operator, meta=meta)
-
-
 def update_shipment(
     session: Session,
     shipment_id: int,