feat(roundtable): 业务链条配置增加管理员权限，管理员可配所有链条

- 后端 store/路由：scope=all（仅管理员）列全量；get/update/delete 加 is_admin 旁路，管理员可操作任意 owner 链条且不转移归属；非管理员请求 all 退化为 mine
- 前端列表页/会商弹窗：管理员多「全部链条」筛选 tab，canManage=isAdmin||isMine 放开发布/设置/删除
- 编辑器：管理员可见发布按钮；按 chainId 找不到本地列表时直接 getChain 拉取（修复管理员从「全部链条」进编辑器空白），并修掉自身无链条时加载卡死的边界

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

offline-backend-20260512/backend/app/gateway/routers/roundtable_chains.py

@@ -6,11 +6,15 @@ following this order. Bound to the requesting user (not the browser), so it
 follows the account across devices/sessions — same model as roundtable drafts.
 
 Routes (prefix ``/api/roundtable-chains``):
-    GET    ""               list current user's chains (full records, incl. seats)
+    GET    ""               list chains (``scope=mine``默认 / ``public`` / ``all`` 仅管理员)
     POST   ""               create a chain
     GET    "/{chain_id}"    one chain
     PUT    "/{chain_id}"    partial update (title / description / seats)
     DELETE "/{chain_id}"    delete
+
+管理员权限：``system_role == "admin"`` 的用户（``_is_admin``）可 list ``scope=all``
+（所有账号的全部链条），并可 get / 编辑 / 发布 / 删除**任意** owner 的链条；非管理员
+仍仅限本人链条（``scope=all`` 退化为 ``mine``）。编辑/删除不转移链条归属（``user_id`` 不变）。
 """
 
 from __future__ import annotations
@@ -131,6 +135,18 @@ def _current_user_id(request: Request) -> str:
     return get_effective_user_id()
 
 
+def _is_admin(request: Request) -> bool:
+    """当前请求是否为管理员。
+
+    认证关闭时 ``request.state.user`` 为 None（单一 default 用户，mine 即 all），
+    按管理员处理（与 menu_overrides 等放行约定一致，无越权风险）。
+    """
+    user = getattr(request.state, "user", None)
+    if user is None:
+        return True
+    return getattr(user, "system_role", None) == "admin"
+
+
 async def _enrich_owner_names(rows: list[dict]) -> None:
     """把每行的 ``owner_id`` 解析成可读用户名（email），写入 ``owner_name``。
 
@@ -269,13 +285,18 @@ async def list_chains(request: Request, scope: str = "mine") -> ChainListRespons
 
     ``scope`` 查询参数(筛选):
       - ``mine``（默认）：仅当前用户自己的链条；
-      - ``public``：所有**已发布**的公共链条（任何账号均可查看 / 选入研讨）。
+      - ``public``：所有**已发布**的公共链条（任何账号均可查看 / 选入研讨）；
+      - ``all``：所有账号的全部链条（**仅管理员**；非管理员请求 ``all`` 退化为 ``mine``）。
     其余值按 ``mine`` 处理。
     """
-    normalized_scope = scope if scope in ("mine", "public") else "mine"
+    is_admin = _is_admin(request)
+    normalized_scope = scope if scope in ("mine", "public", "all") else "mine"
+    # 非管理员请求 all → 退化为 mine，绝不越权。
+    if normalized_scope == "all" and not is_admin:
+        normalized_scope = "mine"
     store = _get_store(request)
     user_id = _current_user_id(request)
-    rows = await store.list_chains(user_id, scope=normalized_scope)
+    rows = await store.list_chains(user_id, scope=normalized_scope, is_admin=is_admin)
     await _enrich_owner_names(rows)
     return ChainListResponse(chains=[ChainResponse(**r) for r in rows])
 
@@ -310,7 +331,7 @@ async def create_chain(request: Request, body: ChainCreateRequest) -> ChainRespo
 async def get_chain(request: Request, chain_id: str) -> ChainResponse:
     store = _get_store(request)
     user_id = _current_user_id(request)
-    row = await store.get_chain(chain_id, user_id)
+    row = await store.get_chain(chain_id, user_id, is_admin=_is_admin(request))
     if row is None:
         raise HTTPException(status_code=404, detail="Chain not found")
     await _enrich_owner_names([row])
@@ -334,7 +355,7 @@ async def update_chain(request: Request, chain_id: str, body: ChainUpdateRequest
     user_id = _current_user_id(request)
     # Distinguish "omitted" from "explicitly sent"; only forward provided fields.
     fields = body.model_dump(exclude_unset=True)
-    row = await store.update_chain(chain_id, user_id, **fields)
+    row = await store.update_chain(chain_id, user_id, is_admin=_is_admin(request), **fields)
     if row is None:
         raise HTTPException(status_code=404, detail="Chain not found")
     await _enrich_owner_names([row])
@@ -345,7 +366,7 @@ async def update_chain(request: Request, chain_id: str, body: ChainUpdateRequest
 async def delete_chain(request: Request, chain_id: str) -> None:
     store = _get_store(request)
     user_id = _current_user_id(request)
-    deleted = await store.delete_chain(chain_id, user_id)
+    deleted = await store.delete_chain(chain_id, user_id, is_admin=_is_admin(request))
     if not deleted:
         raise HTTPException(status_code=404, detail="Chain not found")