新增 pc-client：畅联 PC 端工程（Electron+React，按确认效果图改造，B-59）

- 基于 openim-electron-demo 改造：工号+密码登录（自研账号服务）、会话列表/聊天窗/通讯录界面重做
- 文字/语音/文件/图片消息、文件拖拽发送、表情面板、一对一语音通话（LiveKit）
- RTC 令牌对接账号服务带鉴权版 /api/rtc_token（Bearer imToken + {room,identity}）
- account-service: CORS Allow-Headers 补 authorization（浏览器/渲染进程跨域调 rtc_token 需要）
- 附本地 mock 账号服务（scripts/mock-account-server.js）与截图联调脚本

pc-client/electron/utils/imsdk.ts

@@ -0,0 +1,22 @@
+import path from "path";
+import os from "os";
+import OpenIMSDKMain from "@openim/electron-client-sdk";
+import { WebContents } from "electron";
+
+export const getLibSuffix = () => {
+  const platform = process.platform;
+  const arch = os.arch();
+  if (platform === "darwin") {
+    return path.join(`mac_${arch === "arm64" ? "arm64" : "x64"}`, "libopenimsdk.dylib");
+  }
+  if (platform === "win32") {
+    return path.join(`win_${arch === "ia32" ? "ia32" : "x64"}`, "libopenimsdk.dll");
+  }
+  return path.join(`linux_${arch === "arm64" ? "arm64" : "x64"}`, "libopenimsdk.so");
+};
+
+export const initIMSDK = (webContents: WebContents) =>
+  new OpenIMSDKMain(
+    path.join(global.pathConfig.imsdkLibPath, getLibSuffix()),
+    webContents,
+  );