fix: cover.py step3 改用 user+template 查找预览任务；删除 generation.py 冗余 rendered_url

P0 修复：预览任务创建时 plan_id 尚未存在，source_edit_plan_id 始终为空，
导致封面生成第三步查找永远匹配不到。改为按 user_id + template_id + is_preview +
status=completed 查找最近预览任务。

技术债：generation.py 复用预览产物分支删除冗余 rendered_url 写入，
统一只写 rendered_storage_key。

新增 repository 方法：list_latest_completed_preview(user_id, template_id)

apps/api/app/api/routes/templates_editor/cover.py

@@ -79,32 +79,32 @@ def editor_generate_cover(
                     exc_info=True,
                 )
 
-    # 第三步：如果还没有，通过 source_edit_plan_id 查找最近完成的预览任务
+    # 第三步：按 user + template 查找最近的已完成预览任务（兜底）
     if not rendered_storage_key:
         try:
             gen_task_repo = SQLAlchemyGenerationTaskRepository(db)
-            preview_tasks = gen_task_repo.list_by_source_edit_plan(plan_id)
-            # 过滤 is_preview=True + is_completed，取最新的
-            completed_preview = None
-            for t in preview_tasks:
-                if getattr(t, "is_preview", False) and t.is_completed:
-                    completed_preview = t
-                    break  # list_by_source_edit_plan 已按创建时间倒序
-            if completed_preview:
+            preview_tasks = gen_task_repo.list_latest_completed_preview(
+                user_id=str(current_user.user.id),
+                template_id=template_id,
+            )
+            if preview_tasks:
+                completed_preview = preview_tasks[0]
                 video_repo = get_generated_video_repository(db)
                 use_case = ListGeneratedVideosByTaskUseCase(video_repo)
                 videos = use_case.execute(completed_preview.id)
                 if videos:
                     rendered_storage_key = getattr(videos[0], "file_url", "") or ""
                     logger.info(
-                        "封面生成: 通过 source_edit_plan_id 找到视频: plan_id=%s task_id=%s",
+                        "封面视频: 通过 user+template 找到预览任务: plan_id=%s template_id=%s task_id=%s",
                         plan_id,
+                        template_id,
                         completed_preview.id,
                     )
         except Exception:
             logger.warning(
-                "封面生成: 通过 source_edit_plan_id 查找视频失败: plan_id=%s",
+                "封面警告: user+template 查找预览任务失败: plan_id=%s template_id=%s",
                 plan_id,
+                template_id,
                 exc_info=True,
             )
 

apps/api/app/api/routes/templates_editor/generation.py

@@ -96,7 +96,6 @@ def generate_editor_draft(
             plan_id,
             {
                 "generation_task_id": reusable_task.id,
-                "rendered_url": rendered_url,
                 "rendered_storage_key": rendered_url,  # 统一用 rendered_storage_key
             },
         )

packages/adapters/sqlalchemy_impl/generation_task_repository.py

@@ -148,6 +148,22 @@ class SQLAlchemyGenerationTaskRepository:
         )
         return [_to_domain(m) for m in models]
 
+    def list_latest_completed_preview(self, user_id: str, template_id: str, limit: int = 1) -> list[GenerationTask]:
+        """按用户+模板查找最近已完成的预览任务。"""
+        models = (
+            self.session.query(GenerationTaskModel)
+            .filter(
+                GenerationTaskModel.created_by_user_id == user_id,
+                GenerationTaskModel.template_id == template_id,
+                GenerationTaskModel.is_preview,
+                GenerationTaskModel.status == "completed",
+            )
+            .order_by(GenerationTaskModel.created_at.desc())
+            .limit(limit)
+            .all()
+        )
+        return [_to_domain(m) for m in models]
+
     def list_by_source_edit_plan(self, plan_id: str) -> list[GenerationTask]:
         models = (
             self.session.query(GenerationTaskModel)