chore(pl): remove unused inventory editable guard after force sync

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/services/pl_dibang_bridge_service.py

@@ -561,11 +561,6 @@ def _inventory_date_editable(db: Session, inventory: DbInboundOutbound) -> bool:
     return True
 
 
-def _inventory_mutable_editable(db: Session, inventory: DbInboundOutbound) -> bool:
-    """未过磅且状态可作废时，可就地更新日期/往来/车牌/数量。"""
-    return _inventory_date_editable(db, inventory)
-
-
 def _find_active_stop_link(
     db: Session,
     *,
@@ -1229,7 +1224,8 @@ def upsert_stop_dibang_links(
 ) -> tuple[list[DibangInventoryLinkResult], list[str]]:
     """按段 upsert 地磅出入库与 link：新建 / 就地更新 / 取消勾选软删。
 
-    返回 (link_results, warnings)。已过磅取消勾选或产品变更时抛 ValueError。
+    返回 (link_results, warnings)。产品/往来变更就地同步（跨月改挂完整逻辑见 Task 3）；
+    已过磅取消勾选时抛 ValueError。
     """
     apply_stop_dibang_options(
         db,