feat(perf,ux): implement performance and UX optimizations

Phase 2: Performance Optimizations
- Implement dynamic imports for non-critical sections
- Add loading skeletons for lazy-loaded components
- Optimize bundle size with code splitting
- Enable SSR for dynamic components

Phase 3: UX Optimizations
- Create ErrorBoundary component for graceful error handling
- Add Toast notification component for user feedback
- Implement success/error notifications in contact form
- Add error handling with user-friendly messages

Files modified:
- src/app/(marketing)/page.tsx: Dynamic imports for sections
- src/app/(marketing)/layout.tsx: Error boundary integration
- src/components/sections/contact-section.tsx: Toast notifications
- src/components/ui/error-boundary.tsx: New error boundary component
- src/components/ui/toast.tsx: New toast notification component

Impact:
- Reduced initial bundle size
- Faster page load times
- Better error handling
- Improved user feedback
- Enhanced user experience

src/components/ui/error-boundary.tsx

@@ -0,0 +1,66 @@
+'use client';
+
+import { Component, ReactNode } from 'react';
+
+interface Props {
+  children: ReactNode;
+  fallback?: ReactNode;
+}
+
+interface State {
+  hasError: boolean;
+  error?: Error;
+}
+
+export class ErrorBoundary extends Component<Props, State> {
+  constructor(props: Props) {
+    super(props);
+    this.state = { hasError: false };
+  }
+
+  static getDerivedStateFromError(error: Error) {
+    return { hasError: true, error };
+  }
+
+  componentDidCatch(error: Error, errorInfo: React.ErrorInfo) {
+    console.error('Error caught by boundary:', error, errorInfo);
+  }
+
+  render() {
+    if (this.state.hasError) {
+      return this.props.fallback || (
+        <div className="flex items-center justify-center min-h-[400px] p-8">
+          <div className="text-center max-w-md">
+            <div className="w-16 h-16 bg-red-100 rounded-full flex items-center justify-center mx-auto mb-4">
+              <svg 
+                className="w-8 h-8 text-red-500" 
+                fill="none" 
+                stroke="currentColor" 
+                viewBox="0 0 24 24"
+              >
+                <path 
+                  strokeLinecap="round" 
+                  strokeLinejoin="round" 
+                  strokeWidth={2} 
+                  d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-3L13.732 4c-.77-1.333-2.694-1.333-3.464 0L3.34 16c-.77 1.333.192 3 1.732 3z" 
+                />
+              </svg>
+            </div>
+            <h2 className="text-2xl font-bold text-[#1C1C1C] mb-4">出错了</h2>
+            <p className="text-[#5C5C5C] mb-6">
+              抱歉，页面出现了问题。请刷新页面重试。
+            </p>
+            <button
+              onClick={() => this.setState({ hasError: false, error: undefined })}
+              className="px-6 py-2.5 bg-[#C41E3A] text-white rounded-lg hover:bg-[#A01830] transition-colors"
+            >
+              重试
+            </button>
+          </div>
+        </div>
+      );
+    }
+
+    return this.props.children;
+  }
+}