@media (max-width: 980px) {
    .app-shell {
        grid-template-columns: 1fr;
        grid-template-areas:
            "topbar"
            "sidebar"
            "main";
        grid-template-rows: 68px auto 1fr;
    }
    .sidebar {
        position: static;
        max-height: none;
        border-right: none;
        border-bottom: 1px solid var(--cinza-borda);
    }
}

@media (max-width: 640px) {
    .main { padding: 20px 16px 40px; }
    .topbar { padding: 0 16px; }
    .topbar-clock { display: none; }
    .login-card { padding: 32px 22px; }
    .cards-grid { grid-template-columns: 1fr; }
}