feat(task): M1 任务域后端与 Web 列表（状态机/乐观锁/视图/搜索）

- item/tag/item_tag/comment/activity 五表迁移，RLS 全覆盖，pg_trgm 子串索引
- 状态机 domain/task.py：非法流转回 5002 并给 allowed，done 写 completed_at
- /workspaces/{ws}/items 列表/详情/新建/改/状态/软删/评论/标签
- 乐观锁 UPDATE...WHERE version，冲突 4009 + current_version
- Web 任务页：视图 tab、快速新建、勾选完成、开工/阻塞、详情事件流、游标分页
- 测试 43 全绿，ruff 干净，Web 构建通过
- 文档：2.Design/API.md 新增，ROADMAP 按已验证口径重写

web/src/lib/types.ts

@@ -38,3 +38,40 @@ export interface Invitation {
   role: Role;
   expires_at: string;
 }
+
+export type ItemStatus = "inbox" | "todo" | "doing" | "done" | "blocked" | "canceled";
+
+export interface Tag {
+  id: string;
+  name: string;
+  color: string;
+}
+
+export interface Item {
+  id: string;
+  kind: "task" | "ticket" | "knowledge";
+  title: string;
+  body_md: string;
+  status: ItemStatus;
+  priority: number;
+  creator_id: string;
+  assignee_id: string | null;
+  due_at: string | null;
+  completed_at: string | null;
+  tags: Tag[];
+  created_at: string;
+  updated_at: string;
+  version: number;
+}
+
+export interface Activity {
+  id: string;
+  action: string;
+  actor_id: string | null;
+  payload: Record<string, unknown> | null;
+  created_at: string;
+}
+
+export interface ItemDetail extends Item {
+  activities: Activity[];
+}