@media (max-width: 640px) {
  #app-header { flex-direction: column; align-items: flex-start; gap: 0.5rem; }
  #app-nav { width: 100%; }
  .nav-link { flex: 1 1 auto; text-align: center; }
  #app-main { padding: 1rem; }
  .data-table { font-size: 0.8rem; }
  .status-cards { grid-template-columns: repeat(2, 1fr); }
}