使用postMessage向iframe传参theme-mode，实现切换子页面主题的功能

子页面的js示例
```
<script>
    // 接收父页面的主题模式
    window.addEventListener('message', function(event) {
        if (event.data.themeMode) {
            var theme = event.data.themeMode;
            // 测试是否正确接受到theme-mode的值
            // console.log('Received theme mode from parent:', theme);
            applyTheme(theme);
        }
    });

    // 定义一个函数来应用主题
    function applyTheme(theme) {
        var body = document.body;
        if (theme === 'dark') {
            body.classList.add("dark-mode");
            document.getElementById("darkModeToggle").checked = true;
        } else {
            body.classList.remove("dark-mode");
            document.getElementById("darkModeToggle").checked = false;
        }
    }
</script>
```

web/src/components/HeaderBar.js

@@ -118,13 +118,19 @@ const HeaderBar = () => {
   useEffect(() => {
     if (theme === 'dark') {
       document.body.setAttribute('theme-mode', 'dark');
+    } else {
+      document.body.removeAttribute('theme-mode');
+    }
+    // 发送当前主题模式给子页面
+    const iframe = document.querySelector('iframe');
+    if (iframe) {
+      iframe.contentWindow.postMessage({ themeMode: theme }, '*');
     }
 
     if (isNewYear) {
       console.log('Happy New Year!');
     }
-  }, []);
-
+  }, [theme]); // 监听 theme-mode 的变化
   return (
     <>
       <Layout>

web/src/pages/Home/index.js

@@ -35,6 +35,19 @@ const Home = () => {
       }
       setHomePageContent(content);
       localStorage.setItem('home_page_content', content);
+
+        // 如果内容是 URL，则发送主题模式
+        if (data.startsWith('https://')) {
+            const iframe = document.querySelector('iframe');
+            if (iframe) {
+                const theme = localStorage.getItem('theme-mode') || 'light';
+                // 测试是否正确传递theme-mode给iframe
+                // console.log('Sending theme-mode to iframe:', theme); 
+                iframe.onload = () => {
+                    iframe.contentWindow.postMessage({ themeMode: theme }, '*');
+                };
+            }
+        }
     } else {
       showError(message);
       setHomePageContent('加载首页内容失败...');