fix: support removing group members

docs/IM-前后端对接文档.md

@@ -2185,6 +2185,7 @@ GET /v1/im/topics/{topic}/message-mutations?since_version={localMutationVersion}
 | `POST /v1/im/groups/{topic}/leave` | `{}` | `{"topic":"grp...","status":"left"}` |
 | `GET /v1/im/groups/{topic}/members?query=&cursor=&mentionable=true` | Query only | `{"topic":"grp...","items":[{"user_id":"usr...","display_name":"张三","group_nickname":"小张","avatar_file_id":"","role":"member","member_status":"active","version":1,"joined_at":"2026-08-20T09:00:00Z","updated_at":"2026-08-20T09:00:00Z","mentionable":true,"acs":{"want":"JRWP","given":"JRWP","mode":"JRWP"}}],"next_cursor":"","sync_mode":"full","permissions":{"can_mention_all":true}}` |
 | `GET /v1/im/groups/{topic}/members/{user_id}` | Path topic/user | `{"topic":"grp...","user_id":"usr...","display_name":"张三","group_nickname":"小张","role":"member","member_status":"active","version":1,"joined_at":"2026-08-20T09:00:00Z","updated_at":"2026-08-20T09:00:00Z","sync_mode":"single","acs":{"want":"JRWP","given":"JRWP","mode":"JRWP"}}` |
+| `DELETE /v1/im/groups/{topic}/members/{user_id}` | Path topic/user；管理员可移除普通成员，群主可移除管理员和普通成员；不能移除群主或自己 | `{"topic":"grp...","user_id":"usr...","status":"left"}` |
 | `GET /v1/im/groups/{topic}/members/{user_id}/profile` | Path topic/user；`topic` 必须是 `grp...`，不能传 `usr...` | `{"topic":"grp...","user_id":"usr...","display_name":"张三","group_nickname":"小张","role":"member","relationship":"friend","capabilities":{"can_send":true,"can_call":true}}` |
 | `POST /v1/im/groups/{topic}/qrcodes` | `{"expires_in_seconds":86400}` | `{"qr_token":"token...","qr_payload":"im://qr?token=...&purpose=join_group","expires_at":"2026-08-21T09:00:00Z","group":{"topic":"grp...","name":"项目群","member_count":2},"group_snapshot":{"topic":"grp...","name":"项目群","member_count":2}}` |
 | `POST /v1/im/groups/{topic}/invitations` | `{"user_ids":["usr..."],"message":"进群一起讨论"}` | `{"topic":"grp...","items":[{"user_id":"usr...","status":"joined","invitation_id":"ginv_1"}]}` |