feat(pl): arrange-qty and overflow checks use product+package key

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

backend/app/api/pl/plan.py

@@ -847,6 +847,7 @@ def count_plans_by_contract(
 def get_contract_product_arrange_qty(
     contract_id: str = Query(..., alias="contractId"),
     product_id: str = Query(..., alias="productId"),
+    package_spec: Optional[str] = Query(default=None, alias="packageSpec"),
     exclude_plan_id: Optional[str] = Query(default=None, alias="excludePlanId"),
     db: Session = Depends(get_db),
     user: DbUserContext = Depends(get_db_current_user),
@@ -860,6 +861,7 @@ def get_contract_product_arrange_qty(
         tenant_no=tenant_no,
         contract_id=contract_id,
         product_id=product_id,
+        package_spec=package_spec,
         exclude_plan_id=exclude_plan_id,
     )