7-3 修复老订单成本核算及业务员尺寸传递

- 定价引擎始终重算cost_price（移除cost==0限制）
- 业务员表单calcDemandResult设置length_m/width_m
- 管理员编辑表格补上需求规格列

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/order_service.py

@@ -237,8 +237,8 @@ class OrderService:
                 "price_tier": getattr(item, "price_tier", None),
             }
 
-            # cost_price 为 0 且有定价规则时，尝试用引擎重算
-            if item_dict["cost_price"] == 0 and item.product_id and item.product_id in rules_map:
+            # 有定价规则且有尺寸数据时，用定价引擎重算 cost_price
+            if item.product_id and item.product_id in rules_map:
                 rule = rules_map[item.product_id]
                 product = products_map.get(item.product_id)
                 product_attrs = {}
@@ -251,7 +251,6 @@ class OrderService:
                         product_attrs["default_width_m"] = float(product.default_width_m)
 
                 user_inputs = {}
-                # 优先使用已存储的 length_m/width_m，否则从 demand_specification 解析
                 lm = getattr(item, "length_m", None)
                 wm = getattr(item, "width_m", None)
                 if lm and wm:

frontend/web-admin/src/views/OrdersPage.vue

@@ -350,6 +350,7 @@
                              style="margin-top: 4px;"/>
                     </td>
                     <td><input v-model="item.specification" type="text" placeholder="规格" class="inline-input"/></td>
+                    <td><input v-model="item.demand_specification" type="text" placeholder="如: 25cm×25cm" class="inline-input"/></td>
                     <td><input v-model="item.unit" type="text" placeholder="单位" class="inline-input"
                                style="width: 60px;"/></td>
                     <td><input v-model.number="item.quantity" type="number" min="1" class="inline-input"

frontend/web-sales/src/views/OrderFormPage.vue

@@ -806,6 +806,8 @@ function calcDemandResult(row) {
     const toM = (v, u) => u === "m" ? v : u === "mm" ? v / 1000 : v / 100;
     const m1 = toM(v1, u1);
     const m2 = toM(v2, u2);
+    row.length_m = m2;
+    row.width_m = m1;
     const area = m1 * m2;
     row._demandResult = `${area.toFixed(4)} m²`;
     row._demandCalcHint = `${v1}${u1} × ${v2}${u2} = ${m1}m × ${m2}m = ${area.toFixed(4)}m²`;