feat(business): 回款管理接口（批次号/手动指定批次/已核算禁改/合计回写）

- 批次 HK 生成；shipment_id 同业务强校验（统一失败面防探测）
- 已核算回款禁改禁删（M3 防重锚点）；payment_days 派生（发货日首日=第 1 天）

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

backend/app/repositories/receipt_repository.py

@@ -0,0 +1,127 @@
+"""回款数据访问：回款行与关联引用（业务号/发货单号/发货日）。
+
+只读写数据并 flush；commit/rollback 与业务异常一律在 service 层。
+
+- 列表与详情统一 join 出 ``business_no / shipment_no / ship_date``，
+  ship_date 供 service 按 ``formula.payment_days`` 派生回款天数 —— 关联
+  引用经本层查询一次供给，service 不再对发货单二次查询
+- shipment_id 是手动指定（可空），发货单关联一律 outerjoin
+"""
+
+from datetime import date
+
+from sqlalchemy import Select, func, select
+from sqlalchemy.orm import Session
+
+from app.models import Business, Receipt, Shipment
+
+
+def get_by_id(session: Session, receipt_id: int) -> Receipt | None:
+    """按主键取回款行（供摘要预取与状态判定；不锁行，写保护锚在业务行）。"""
+    return session.get(Receipt, receipt_id)
+
+
+def get_with_refs(
+    session: Session, receipt_id: int
+) -> tuple[Receipt, str, str | None, date | None] | None:
+    """回款行 + 业务号 + 发货单号 + 发货日（DTO 与 payment_days 派生共用）。
+
+    business 主表为 inner join（FK NOT NULL，业务与回款同存亡）；发货单
+    可未指定，outerjoin 后 shipment_no / ship_date 可能为 None。
+    """
+    row = session.execute(
+        select(Receipt, Business.business_no, Shipment.shipment_no, Shipment.ship_date)
+        .join(Business, Business.id == Receipt.business_id)
+        .outerjoin(Shipment, Shipment.id == Receipt.shipment_id)
+        .where(Receipt.id == receipt_id)
+    ).first()
+    return row
+
+
+def get_shipment(session: Session, shipment_id: int) -> Shipment | None:
+    """按主键取发货单（同业务强校验的只读预查；FK RESTRICT 为最终防线）。"""
+    return session.get(Shipment, shipment_id)
+
+
+def _apply_filters(
+    stmt: Select,
+    *,
+    business_id: int | None,
+    date_from: date | None,
+    date_to: date | None,
+    is_barter: int | None,
+    settlement_status: int | None,
+) -> Select:
+    """回款列表的筛选条件（全部落在 Receipt 自身列上）。"""
+    if business_id is not None:
+        stmt = stmt.where(Receipt.business_id == business_id)
+    if date_from is not None:
+        stmt = stmt.where(Receipt.receipt_date >= date_from)
+    if date_to is not None:
+        stmt = stmt.where(Receipt.receipt_date <= date_to)
+    if is_barter is not None:
+        stmt = stmt.where(Receipt.is_barter == is_barter)
+    if settlement_status is not None:
+        stmt = stmt.where(Receipt.settlement_status == settlement_status)
+    return stmt
+
+
+def list_receipts(
+    session: Session,
+    *,
+    offset: int,
+    limit: int,
+    business_id: int | None,
+    date_from: date | None,
+    date_to: date | None,
+    is_barter: int | None,
+    settlement_status: int | None,
+) -> list[tuple[Receipt, str, str | None, date | None]]:
+    """分页查询回款（附业务号/发货单号/发货日），按 id 倒序。"""
+    stmt = _apply_filters(
+        select(Receipt, Business.business_no, Shipment.shipment_no, Shipment.ship_date)
+        .join(Business, Business.id == Receipt.business_id)
+        .outerjoin(Shipment, Shipment.id == Receipt.shipment_id),
+        business_id=business_id,
+        date_from=date_from,
+        date_to=date_to,
+        is_barter=is_barter,
+        settlement_status=settlement_status,
+    )
+    return list(
+        session.execute(stmt.order_by(Receipt.id.desc()).offset(offset).limit(limit)).all()
+    )
+
+
+def count_receipts(
+    session: Session,
+    *,
+    business_id: int | None,
+    date_from: date | None,
+    date_to: date | None,
+    is_barter: int | None,
+    settlement_status: int | None,
+) -> int:
+    """回款总数（筛选条件与列表共用同一 apply_filters，防两侧口径漂移）。"""
+    stmt = _apply_filters(
+        select(func.count()).select_from(Receipt),
+        business_id=business_id,
+        date_from=date_from,
+        date_to=date_to,
+        is_barter=is_barter,
+        settlement_status=settlement_status,
+    )
+    return int(session.execute(stmt).scalar_one())
+
+
+def create(session: Session, receipt: Receipt) -> Receipt:
+    """新增回款行。只 flush 以取得自增 id，编号唯一键冲突由 service 兜底。"""
+    session.add(receipt)
+    session.flush()
+    return receipt
+
+
+def delete(session: Session, receipt: Receipt) -> None:
+    """物理删除回款行（已核算与否的准入判定在 service 层）。"""
+    session.delete(receipt)
+    session.flush()