.sidebar {
            width: 260px;
            background: #343a40;
            color: #fff;
            position: fixed;
            top: 0;
            left: -260px; /* 초기에는 숨김 */
            height: 100vh;
            padding-top: 64px; /* 헤더 높이만큼 사이드바 내용 시작 위치 조정 */
            box-sizing: border-box;
            z-index: 1035;
            transition: left 0.3s;
            overflow-y: auto;
        }
        .sidebar.show {
            left: 0;
        }
        .sidebar .nav-link {
            color: #adb5bd;
            border-radius: 0;
            padding-left: 2rem;
        }
        .sidebar .nav-link.active,
        .sidebar .nav-link:focus,
        .sidebar .nav-link:hover {
            color: #fff;
            background: #495057;
            text-decoration: none;
        }
        .sidebar .sidebar-heading {
            font-size: 0.95rem;
            padding: 1rem 1.5rem 0.5rem 1.5rem;
            color: #ced4da;
            letter-spacing: 0.05em;
        }
        .sidebar .nav {
            margin-bottom: 2rem;
        }
        .sidebar .nav-item {
            margin-bottom: 0.2rem;
        }
        .sidebar-close {
            position: absolute;
            top: 1rem;
            right: 1rem;
            color: #adb5bd;
            background: none;
            border: none;
            font-size: 1.5rem;
        }
        .sidebar-close:focus {
            outline: none;
        }
        .sidebar-toggle {
            background: #343a40;
            border: none;
            color: #fff;
            font-size: 1.5rem;
            padding: 0.5rem 0.8rem;
            border-radius: 0.3rem;
            transition: background 0.2s;
            display: flex;
            align-items: center;
        }
        .sidebar-toggle:hover,
        .sidebar-toggle:focus {
            background: #495057;
            color: #fff;
            outline: none;
        }
        .header {
            height: 64px;
            background: #fff;
            border-bottom: 1px solid #dee2e6;
            display: flex;
            align-items: center;
            justify-content: space-between;
            position: fixed;
            top: 0;
            left: 0;
            right: 0;
            z-index: 1030;
            padding: 0 1.5rem;
        }
        .header-left {
            display: flex;
            align-items: center;
        }
        .header-center {
            position: absolute;
            left: 50%;
            transform: translateX(-50%);
            font-weight: bold;
            font-size: 1.5rem;
            letter-spacing: 0.05em;
            color: #343a40;
            user-select: none;
        }
        .header-right {
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }
        .main-content { /* 실제 페이지 컨텐츠가 표시될 영역 */
            margin-top: 64px; /* 헤더 높이만큼 마진 */
            padding: 1.5rem;
            transition: margin-left 0.3s;
        }
        .sidebar.show ~ .main-content { /* 사이드바 열렸을 때 메인 컨텐츠의 왼쪽 마진 */
            margin-left: 260px;
        }
        @media (max-width: 991.98px) {
             .sidebar.show ~ .main-content {
                margin-left: 220px;
            }
        }