feat: 错误监控面板、生成通知、社区搜索、任务队列优化

- AdminMonitor: admin用户可见的客户端错误实时监控面板，右下角浮窗
- generationNotifier: 生成完成浏览器通知 + 站内Toast
- CommunityPage: 新增搜索框，标题/描述/标签模糊匹配，防抖300ms
- App.tsx: 全局unhandled error/rejection监听上报
- WorkbenchPage: 任务并发提示改为显示当前任务数
- serverConnection: 后端client-errors路由注册
- WelcomeSplash: 欢迎按钮全程显示

Co-Authored-By: Claude Code <noreply@anthropic.com>

src/api/keyServerClient.ts

@@ -928,4 +928,9 @@ export const keyServerClient = {
       method: "DELETE",
     });
   },
+
+  async getClientErrors(page = 1): Promise<{ items: unknown[]; total: number }> {
+    const data = await request<{ items: unknown[]; total: number }>(`/client-errors?page=${page}`);
+    return data;
+  },
 };