/* ============================================================
   Layout — App Shell (CSS Grid)
   ============================================================ */

.app-shell {
    display: grid;
    grid-template-columns: var(--sidebar-width) 1fr;
    grid-template-rows: var(--header-height) 1fr auto;
    grid-template-areas:
        "sidebar header"
        "sidebar main"
        "sidebar footer";
    min-height: 100vh;
}

/* --- Sidebar --- */
.sidebar {
    grid-area: sidebar;
    position: sticky;
    top: 0;
    height: 100vh;
    background: linear-gradient(180deg, var(--bg-sidebar) 0%, var(--bg-sidebar-end) 100%);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    overflow-y: auto;
    z-index: var(--z-sidebar);
}

.sidebar-brand {
    padding: var(--space-6) var(--space-5);
    border-bottom: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-2);
}

.sidebar-brand img {
    height: 40px;
    filter: brightness(0) invert(1);
}

[data-theme="light"] .sidebar-brand img {
    filter: none;
}

[data-theme="light"] .sidebar {
    border-right: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
}

[data-theme="light"] .app-header {
    background: rgba(244,245,247,0.85);
}

.sidebar-brand .app-name {
    font-size: var(--text-xs);
    color: var(--text-muted);
    text-align: center;
    line-height: var(--leading-tight);
}

.sidebar-nav {
    list-style: none;
    padding: var(--space-3) var(--space-3);
    flex: 1;
}

.sidebar-nav li { margin-bottom: var(--space-1); }

.sidebar-nav a {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-size: var(--text-sm);
    font-weight: var(--fw-medium);
    transition: all var(--duration-fast) var(--ease);
    position: relative;
}

.sidebar-nav a:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.sidebar-nav a.active {
    background: var(--primary-muted);
    color: var(--primary);
}

.sidebar-nav a.active::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 3px;
    height: 60%;
    background: var(--primary);
    border-radius: 0 3px 3px 0;
}

.sidebar-nav .nav-icon {
    width: 20px;
    height: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    flex-shrink: 0;
}

.sidebar-footer {
    padding: var(--space-3);
    border-top: 1px solid var(--border);
    margin-top: auto;
}

/* --- Header --- */
.app-header {
    grid-area: header;
    position: sticky;
    top: 0;
    height: var(--header-height);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--space-6);
    background: rgba(15,17,23,0.8);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    z-index: var(--z-header);
}

.app-header .page-title {
    font-size: var(--text-lg);
    font-weight: var(--fw-semibold);
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.app-header .header-actions {
    display: flex;
    align-items: center;
    gap: var(--space-4);
}

.app-header .user-info {
    font-size: var(--text-sm);
    color: var(--text-muted);
}

/* --- Main Content --- */
.app-main {
    grid-area: main;
    overflow-y: auto;
    padding: var(--space-6);
}

.app-main > .view-container {
    max-width: var(--content-max-width);
    margin: 0 auto;
}

/* --- Footer --- */
.app-footer {
    grid-area: footer;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-3) var(--space-6);
    font-size: var(--text-xs);
    color: var(--text-dimmed);
    border-top: 1px solid var(--border);
}

/* --- Mobile Sidebar Toggle --- */
.sidebar-toggle {
    display: none;
}

@media (max-width: 991px) {
    .app-shell {
        grid-template-columns: 1fr;
        grid-template-areas:
            "header"
            "main"
            "footer";
    }

    .sidebar {
        position: fixed;
        left: 0;
        top: 0;
        width: var(--sidebar-width);
        transform: translateX(-100%);
        transition: transform var(--duration-base) var(--ease);
        box-shadow: var(--shadow-lg);
    }

    .sidebar.open {
        transform: translateX(0);
    }

    .sidebar-overlay {
        display: none;
        position: fixed;
        inset: 0;
        background: rgba(0,0,0,0.5);
        z-index: calc(var(--z-sidebar) - 1);
    }

    .sidebar.open ~ .sidebar-overlay {
        display: block;
    }

    .sidebar-toggle {
        display: flex;
        align-items: center;
        justify-content: center;
        width: 36px;
        height: 36px;
        border-radius: var(--radius);
        color: var(--text-primary);
        font-size: 1.25rem;
    }

    .sidebar-toggle:hover {
        background: var(--bg-hover);
    }

    .app-main {
        padding: var(--space-4);
    }
}

@media (max-width: 575px) {
    .app-header {
        padding: 0 var(--space-4);
    }
    .app-main {
        padding: var(--space-3);
    }
}