feat: add agora rtc token join endpoint

docs/IM-前后端对接文档.md

@@ -2068,9 +2068,12 @@ X-MeetingIM-APIKey: <预置的普通 API Key>
 | --- | --- | --- |
 | WebSocket 发起通话 | `{"pub":{"id":"call-1","topic":"p2p...","head":{"mime":"application/json","webrtc":"started","x-im-type":"call"},"content":{"callId":"call_1","callType":"audio","audio":true,"video":false}}}` | `{"ctrl":{"id":"call-1","code":202,"params":{"seq":12}}}` |
 | WebSocket 通话事件 | `{"note":{"topic":"p2p...","what":"call","event":"accept","seq":12,"payload":{"callId":"call_1"}}}` | 对端收到 `{"info":{"topic":"p2p...","what":"call","event":"accept","seq":12,"payload":{"callId":"call_1"}}}` |
+| `POST /v1/im/calls/rtc-join` | `{"topic":"p2p...","call_id":"call_1","seq":12,"call_type":"audio","role":"caller"}` | `{"provider":"agora","auth_mode":"token","app_id":"声网 App ID","channel_name":"call_call_1","uid":"usr...","token":"007eJx...","token_expires_at":"2026-09-02T10:00:00Z","call_id":"call_1","topic":"p2p...","seq":12,"call_type":"audio","role":"caller"}` |
 | `GET /v1/im/calls?limit=20&cursor=` | Query only | `{"items":[{"call_id":"call_1","topic":"p2p...","seq":12,"call_type":"audio","status":"finished","started_at":"2026-08-20T09:00:00Z","duration_ms":60000,"peer":{"user_id":"usr...","display_name":"张三"}}],"next_cursor":""}` |
 | `GET /v1/im/calls/{topic}?cursor=` | Path topic | `{"topic":"p2p...","items":[{"call_id":"call_1","seq":12,"status":"missed","call_type":"video","created_at":"2026-08-20T09:00:00Z"}],"next_cursor":""}` |
 
+声网模式下，新客户端在发起方收到 `ctrl.params.seq` 后、被叫方点击接听后，分别调用 `POST /v1/im/calls/rtc-join` 获取 `app_id/channel_name/uid/token`。当前按正式 `token` 模式接入，后端使用 `im_shengwang` 分组中的 `agora_app_certificate` 生成 RTC Token。客户端不接触 `app_certificate`、`customer_id`、`customer_secret`，也不再通过 IM WebSocket 交换 SDP/ICE，音视频媒体协商和传输由声网 RTC SDK 完成。
+
 ## 9. 企业工作台与办公协同
 
 ### 9.1 工作台.png