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/App.tsx

@@ -16,6 +16,8 @@ import {
 } from "@ant-design/icons";
 import { lazy, Suspense, useCallback, useEffect, useMemo, useRef } from "react";
 import ErrorBoundary from "./components/ErrorBoundary";
+import { reportError } from "./utils/errorReporting";
+import { initNotificationPermission } from "./utils/generationNotifier";
 import PageTransition from "./components/PageTransition";
 import ToastContainer from "./components/toast/ToastContainer";
 import { aiGenerationClient } from "./api/aiGenerationClient";
@@ -282,6 +284,25 @@ function App() {
     }
   }, []);
 
+  // Pre-warm notification permission (lazy, on first click)
+  useEffect(() => { initNotificationPermission(); }, []);
+
+  // Global unhandled error / rejection listeners — report to server
+  useEffect(() => {
+    const handleUnhandled = (event: ErrorEvent) => {
+      reportError(event.error || new Error(event.message), "unhandled");
+    };
+    const handleRejection = (event: PromiseRejectionEvent) => {
+      reportError(event.reason instanceof Error ? event.reason : new Error(String(event.reason)), "rejection");
+    };
+    window.addEventListener("error", handleUnhandled);
+    window.addEventListener("unhandledrejection", handleRejection);
+    return () => {
+      window.removeEventListener("error", handleUnhandled);
+      window.removeEventListener("unhandledrejection", handleRejection);
+    };
+  }, []);
+
   // Initialize canvasWorkflow if null
   useEffect(() => {
     if (!canvasWorkflow) {