fix(core): 商品详情卖点可编辑+去假数据 / 出图后不再整页重载 / 图片长效缓存

- 商品详情页核心卖点:编辑态原是纯静态文本、且 save 不提交 selling_points,
  既改不了也存不了;改为可改/删/回车增,save 带 selling_points 一起 PATCH。
- 去掉详情页 name/cat/target/卖点 的「设计稿假数据」fallback —— 商品没卖点
  时不再凭空显示护肤品卖点,空值显示「未填写」。
- 出图成功后 submitAndPollAsset 不再整页全量 loadData(十几个 setState 触发
  全页大重渲染),只刷当前项目详情 + 轻量刷余额。
- TOS 上传对象加 Cache-Control: immutable 长效强缓存,重渲染不再重拉图。
- products 序列化器内嵌商品图/封面 preview_url(并修回错位的 read_only_fields)。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

core/backend/apps/projects/views.py

@@ -282,11 +282,32 @@ class ProjectViewSet(TeamScopedViewSetMixin, ModelViewSet):
     @action(detail=True, methods=["post"], url_path="attach-base-asset")
     @transaction.atomic
     def attach_base_asset(self, request, pk=None):
-        """流程步骤4 · 用演员库现有资产替换某基础资产卡:把团队内现有 Asset 挂为该组候选并采用。"""
+        """流程步骤4 · 用演员库现有资产替换某基础资产卡:把团队内现有 Asset 挂为该组候选并采用。
+        seed 占位卡还没有 group,此时不传 group_id,改传 kind+label:按 label 命中同实体组,没有则据 label 建组再挂(不出图)。"""
         project = self.get_object()
-        group = BaseAssetGroup.objects.select_for_update().filter(project=project, id=request.data.get("group_id")).first()
-        if group is None:
-            return Response({"detail": "group not found"}, status=status.HTTP_404_NOT_FOUND)
+        group = None
+        group_id = request.data.get("group_id")
+        if group_id:
+            group = BaseAssetGroup.objects.select_for_update().filter(project=project, id=group_id).first()
+            if group is None:
+                return Response({"detail": "group not found"}, status=status.HTTP_404_NOT_FOUND)
+        else:
+            # 无 group(seed 占位卡):据 kind+label 复用/新建实体组,把所选演员资产挂成该 tag 的立绘
+            kind = request.data.get("kind")
+            if kind not in BaseAssetGroup.Kind.values:
+                return Response({"detail": "group_id or valid kind is required"}, status=status.HTTP_400_BAD_REQUEST)
+            label = str(request.data.get("label") or "").strip()
+            # 按 label 命中同实体组(排除三视图组);商品=该项目唯一非三视图组;都没有则据 label 新建
+            candidates = [g for g in project.base_asset_groups.filter(kind=kind).order_by("created_at")
+                          if not (g.metadata or {}).get("triview_of")]
+            if kind == BaseAssetGroup.Kind.PRODUCT:
+                group = candidates[0] if candidates else None
+            elif label:
+                group = next((g for g in candidates if (g.metadata or {}).get("label") == label), None)
+            if group is None:
+                group_meta = {"label": label} if label else {}
+                group = BaseAssetGroup.objects.create(project=project, kind=kind, metadata=group_meta)
+            group = BaseAssetGroup.objects.select_for_update().get(id=group.id)
         asset = Asset.objects.filter(team=project.team, id=request.data.get("asset_id")).first()
         if asset is None:
             return Response({"detail": "asset not found"}, status=status.HTTP_404_NOT_FOUND)