feat(task): 批量改状态与看板数据接口

- POST /items/batch-status：逐条成败，不做全回滚；拖 10 条里 1 条冲突不该让另 9 条白干
- GET /items/board：四列一次取全，收件箱不进看板
- 修：/items/board 被 /{item_id} 抢先匹配导致 422
- 新增向量库配置项（M3 用，独立实例，不动 fnsvr-01）
- 3 个新测试，全量 46 passed

backend/app/api/items.py

@@ -361,6 +361,60 @@ async def list_items(
     )
 
 
+@router.get("/board", summary="看板：按状态分列的最近任务")
+async def board(
+    ctx: MemberDep,
+    session: SessionDep,
+    per_column: Annotated[int, Query(ge=1, le=100)] = 30,
+) -> dict:
+    """一屏拖动需要的数据，一次拿全。
+
+    每列按"截止时间早的在前、没有截止时间的靠后"排，其次按更新时间。
+    只取 `per_column` 条：看板是"手上正在做的"，不是全量列表。
+    """
+    columns: dict[str, list[dict[str, Any]]] = {}
+    statuses = ("todo", "doing", "blocked", "done")
+    rows = (
+        (
+            await session.execute(
+                select(Item)
+                .where(
+                    Item.workspace_id == ctx.ws_id,
+                    Item.status.in_(statuses),
+                    Item.deleted_at.is_(None),
+                )
+                .order_by(
+                    Item.due_at.asc().nulls_last(),
+                    Item.updated_at.desc(),
+                    Item.id.desc(),
+                )
+                .limit(per_column * len(statuses))
+            )
+        )
+        .scalars()
+        .all()
+    )
+
+    by_id = {row.id: row for row in rows}
+    tag_map = await _tags_of(session, ctx.ws_id, list(by_id))
+    for status in statuses:
+        columns[status] = [
+            _item_out(row, tag_map.get(row.id)) for row in rows if row.status == status
+        ][:per_column]
+    return ok(
+        {
+            "columns": columns,
+            "order": list(statuses),
+            "labels": {
+                "todo": "待办",
+                "doing": "进行中",
+                "blocked": "被阻塞",
+                "done": "已完成",
+            },
+        }
+    )
+
+
 @router.get("/{item_id}", summary="任务详情（含最近 50 条事件）")
 async def get_item(item_id: uuid.UUID, ctx: MemberDep, session: SessionDep) -> dict:
     item = await _load_item(session, ctx.ws_id, item_id)
@@ -423,6 +477,85 @@ async def create_item(body: CreateItemIn, ctx: MemberDep, session: SessionDep) -
     return ok(_item_out(item, tags.get(item.id)), message="已创建")
 
 
+class BatchStatusItemIn(BaseModel):
+    id: uuid.UUID
+    version: int
+
+
+class BatchStatusIn(BaseModel):
+    status: str
+    items: list[BatchStatusItemIn] = Field(min_length=1, max_length=50)
+
+
+@router.post("/batch-status", summary="批量改状态（逐条返回成败）")
+async def batch_status(body: BatchStatusIn, ctx: MemberDep, session: SessionDep) -> dict:
+    """看板多选拖拽用。
+
+    不做"全成功或全回滚"：拖 10 条里有 1 条被同事改过，其余 9 条应当照样生效，
+    失败的那条单独告诉前端原因。全回滚会让用户白干一次，而且更难解释。
+    """
+    if body.status not in ALL_STATUSES:
+        raise AppError(ErrorCode.BAD_REQUEST, f"未知状态：{body.status}")
+
+    now = datetime.now(timezone.utc)
+    updated: list[dict[str, Any]] = []
+    failed: list[dict[str, Any]] = []
+
+    for entry in body.items:
+        try:
+            item = await _load_item(session, ctx.ws_id, entry.id)
+        except AppError as exc:
+            failed.append({"id": str(entry.id), "code": int(exc.code), "message": exc.message})
+            continue
+
+        if item.status == body.status:
+            updated.append({"id": str(item.id), "version": item.version, "unchanged": True})
+            continue
+
+        try:
+            ensure_transition(item.status, body.status)
+        except AppError as exc:
+            failed.append(
+                {
+                    "id": str(entry.id),
+                    "code": int(exc.code),
+                    "message": exc.message,
+                    "allowed": (exc.details or {}).get("allowed"),
+                }
+            )
+            continue
+
+        previous = item.status
+        fields: dict[str, Any] = {"status": body.status, "completed_at": None}
+        apply_status(fields, body.status, now=now)
+        try:
+            item = await _apply_update(
+                session,
+                item,
+                version=entry.version,
+                values={"status": fields["status"], "completed_at": fields["completed_at"]},
+                actor_id=ctx.user.id,
+                action="status_changed",
+                payload={"from": previous, "to": body.status, "batch": True},
+            )
+        except AppError as exc:
+            failed.append(
+                {
+                    "id": str(entry.id),
+                    "code": int(exc.code),
+                    "message": exc.message,
+                    "current_version": (exc.details or {}).get("current_version"),
+                }
+            )
+            continue
+        updated.append({"id": str(item.id), "version": item.version, "unchanged": False})
+
+    return ok(
+        {"updated": updated, "failed": failed},
+        message=f"已更新 {len(updated)} 条，{len(failed)} 条未生效",
+    )
+
+
 @router.patch("/{item_id}", summary="修改任务字段（乐观锁）")
 async def update_item(
     item_id: uuid.UUID, body: UpdateItemIn, ctx: MemberDep, session: SessionDep