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/patches/@ckeditor+ckeditor5-ui+43.0.0.patch

@@ -0,0 +1,42 @@
+diff --git a/node_modules/@ckeditor/ckeditor5-ui/src/editorui/poweredby.js b/node_modules/@ckeditor/ckeditor5-ui/src/editorui/poweredby.js
+index 191aba1..324f6d2 100644
+--- a/node_modules/@ckeditor/ckeditor5-ui/src/editorui/poweredby.js
++++ b/node_modules/@ckeditor/ckeditor5-ui/src/editorui/poweredby.js
+@@ -112,12 +112,9 @@ export default class PoweredBy extends /* #__PURE__ */ DomEmitterMixin() {
+             if (!this._balloonView) {
+                 this._createBalloonView();
+             }
+-            this._balloonView.pin(attachOptions);
++            // this._balloonView.pin(attachOptions);
+         }
+     }
+-    /**
+-     * Hides the "powered by" balloon if already visible.
+-     */
+     _hideBalloon() {
+         if (this._balloonView) {
+             this._balloonView.unpin();
+diff --git a/node_modules/@ckeditor/ckeditor5-ui/src/icon/iconview.js b/node_modules/@ckeditor/ckeditor5-ui/src/icon/iconview.js
+index dd6d2ed..7af8e61 100644
+--- a/node_modules/@ckeditor/ckeditor5-ui/src/icon/iconview.js
++++ b/node_modules/@ckeditor/ckeditor5-ui/src/icon/iconview.js
+@@ -42,17 +42,14 @@ class IconView extends View {
+             }
+         });
+     }
+-    /**
+-     * @inheritDoc
+-     */
+     render() {
+         super.render();
+-        this._updateXMLContent();
++        // this._updateXMLContent();
+         this._colorFillPaths();
+         // This is a hack for lack of innerHTML binding.
+         // See: https://github.com/ckeditor/ckeditor5-ui/issues/99.
+         this.on('change:content', () => {
+-            this._updateXMLContent();
++            // this._updateXMLContent();
+             this._colorFillPaths();
+         });
+         this.on('change:fillColor', () => {