试一下代码

// 初始化主题时添加验证
function initTheme() {
    const saved = localStorage.getItem('theme');
    // 仅允许light/dark两种值，防止篡改
    const validThemes = ['light', 'dark'];
    const theme = validThemes.includes(saved) ? saved : getSystemTheme();
    if (theme === 'dark') {
        html.setAttribute('data-theme', 'dark');
        themeBtn.textContent = '☀️';
    } else {
        html.removeAttribute('data-theme');
        themeBtn.textContent = '🌙';
    }
}

// 存储时添加验证
themeBtn.addEventListener('click', () => {
    const isDark = html.hasAttribute('data-theme');
    const newTheme = isDark ? 'light' : 'dark';
    if (['light', 'dark'].includes(newTheme)) { // 验证值合法性
        if (isDark) {
            html.removeAttribute('data-theme');
            themeBtn.textContent = '🌙';
        } else {
            html.setAttribute('data-theme', 'dark');
            themeBtn.textContent = '☀️';
        }
        localStorage.setItem('theme', newTheme);
    }
});

我好困