/* CSS cho chế độ tối */
body {
    transition: background-color 0.5s, color 0.5s;
}
body.dark-mode {
    background-color: #121212;
    color: #ffffff;
}

body.dark-mode .form-control {
    background-color: #444;
    color: #fff;
    border-color: #555;
}

body.dark-mode .btn-light {
    background-color: #f1f1f1;
    color: #333;
}

body.dark-mode .btn-dark {
    background-color: #333;
    color: #fff;
}