feat(pl): allow optional stop/product ids on plan write bodies.

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

backend/app/schemas/pl/plan.py

@@ -53,6 +53,7 @@ class PlanProductBase(BaseModel):
 
 
 class PlanProductCreate(PlanProductBase):
+    id: Optional[str] = Field(default=None, description="已有计划产品行ID；编辑回传以保留主键")
     model_config = {"populate_by_name": True}
 
 
@@ -141,6 +142,7 @@ class PlanStopProductRead(PlanStopProductBody):
 
 
 class PlanLoadBody(BaseModel):
+    id: Optional[str] = Field(default=None, description="已有段ID；编辑回传以保留主键")
     customer_id: Optional[str] = Field(default=None, alias="customerId", description="装货客户ID")
     customer_name: Optional[str] = Field(default=None, max_length=200, alias="customerName", description="装货客户名称")
     address: Optional[str] = Field(default=None, max_length=500, description="装货地址")
@@ -160,6 +162,7 @@ class PlanLoadBody(BaseModel):
 
 
 class PlanDeliveryBody(BaseModel):
+    id: Optional[str] = Field(default=None, description="已有段ID；编辑回传以保留主键")
     seq: int = Field(default=1, description="顺序号（打印、链接展示）")
     customer_id: Optional[str] = Field(default=None, alias="customerId", description="送货客户ID")
     customer_name: Optional[str] = Field(default=None, max_length=200, alias="customerName", description="送货客户名称")

docs/superpowers/specs/2026-09-05-pl-stop-stable-id-reuse-links-design.md

@@ -1,7 +1,7 @@
 # 运输计划段次稳定 ID + 外围单据就地复用
 
 **日期：** 2026-09-05  
-**状态：** 待审阅（brainstorming 已确认方案 3）  
+**状态：** 已确认  
 **触发案例：** 生产 `PO20260904024` — 库内已有地磅单，详情「送货」段显示「暂无关联地磅单」  
 **相关：** `2026-08-26-pl-multi-stop-redesign-design.md`、`2026-08-30-pl-plan-save-sync-dibang-date-design.md`、`2026-06-20-pl-arrange-dibang-design.md`