feat: add error boundary and loading spinner components with SWR integration

frontend/components/ErrorBoundary.js

@@ -0,0 +1,56 @@
+import React from 'react';
+import { Icon } from './icons';
+
+class ErrorBoundary extends React.Component {
+  constructor(props) {
+    super(props);
+    this.state = { hasError: false, error: null };
+  }
+
+  static getDerivedStateFromError(error) {
+    return { hasError: true, error };
+  }
+
+  componentDidCatch(error, errorInfo) {
+    console.error('ErrorBoundary caught error:', error, errorInfo);
+  }
+
+  handleReload = () => {
+    window.location.reload();
+  };
+
+  handleGoHome = () => {
+    window.location.href = '/';
+  };
+
+  render() {
+    if (this.state.hasError) {
+      return (
+        <div className="error-boundary">
+          <div className="error-boundary__content">
+            <Icon name="info" size={48} />
+            <h2>出错了</h2>
+            <p>抱歉，应用遇到了问题。</p>
+            {process.env.NODE_ENV === 'development' && (
+              <pre className="error-boundary__details">
+                {this.state.error?.toString()}
+              </pre>
+            )}
+            <div className="error-boundary__actions">
+              <button onClick={this.handleGoHome} className="btn btn-secondary">
+                返回首页
+              </button>
+              <button onClick={this.handleReload} className="btn btn-primary">
+                重新加载
+              </button>
+            </div>
+          </div>
+        </div>
+      );
+    }
+
+    return this.props.children;
+  }
+}
+
+export default ErrorBoundary;

frontend/components/LoadingSpinner.js

@@ -0,0 +1,10 @@
+import { Icon } from './icons';
+
+export default function LoadingSpinner({ size = 24, text = '加载中...' }) {
+  return (
+    <div className="loading-spinner">
+      <Icon name="spinner" size={size} className="is-spinning" />
+      {text && <span>{text}</span>}
+    </div>
+  );
+}