feat(gateway): 补齐桌面端高级媒体直连接口

新增图片矢量化、视频超分、每日用量、计价与任务隔离能力，并通过环境变量解析平台凭据。

已通过 Go 全量门禁、迁移检查、镜像构建以及 Vectorizer 五格式和 Topaz 3 秒视频真实 DEV 验收。

apps/api/internal/runner/task_cancel.go

@@ -211,6 +211,13 @@ func taskAccessibleToUser(task store.GatewayTask, user *auth.User) bool {
 	return userID != "" && strings.TrimSpace(task.UserID) == userID
 }
 
+// TaskAccessibleToUser applies the same ownership boundary to every public
+// task surface. API-key requests are deliberately scoped to the exact key,
+// while JWT requests may see the current gateway user's tasks.
+func TaskAccessibleToUser(task store.GatewayTask, user *auth.User) bool {
+	return taskAccessibleToUser(task, user)
+}
+
 func gatewayUserIDForAuth(user *auth.User) string {
 	if user == nil {
 		return ""