.app-shell {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  grid-template-rows: var(--topbar-h) 1fr;
  grid-template-areas: "topbar topbar" "sidebar main";
  height: 100vh;
}
@media (max-width: 860px) {
  .app-shell { grid-template-columns: 0 1fr; }
  .sidebar.is-open { transform: translateX(0); }
}

.topbar {
  grid-area: topbar;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: 0 var(--space-4);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  z-index: 10;
}
.topbar-brand { font-weight: 700; font-size: var(--fs-lg); display: flex; align-items: center; gap: var(--space-2); color: var(--color-text); }
.brand-mark { color: var(--color-brand-accent); font-size: 20px; }

/* Left sidebar navigation, grouped into sections (Sales, Activities), matching
   Zoho CRM's actual dark-navy left-nav (see contacts-module-spec.md section 2). */
.sidebar {
  grid-area: sidebar;
  background: var(--sidebar-bg);
  overflow-y: auto;
  transition: transform 0.15s ease;
  padding-top: var(--space-2);
}
@media (max-width: 860px) {
  .sidebar { position: fixed; top: var(--topbar-h); bottom: 0; left: 0; width: var(--sidebar-w); transform: translateX(-100%); z-index: 20; }
}
.sidebar-nav { display: flex; flex-direction: column; gap: 1px; padding: 0 var(--space-2); }
.sidebar-group-label {
  padding: var(--space-3) var(--space-4) var(--space-1);
  font-size: var(--fs-md);
  font-weight: 500;
  color: var(--sidebar-text);
}
.nav-item {
  display: flex; align-items: center;
  padding: 8px var(--space-4);
  margin: 0 var(--space-2);
  border-radius: var(--radius-sm);
  color: var(--sidebar-text);
  font-size: var(--fs-sm);
}
.nav-item:hover { background: rgba(255, 255, 255, 0.06); color: var(--sidebar-text-active); }
.nav-item[aria-current="page"] { background: var(--sidebar-active-bg); color: var(--sidebar-text-active); font-weight: 500; }
.nav-dot { width: 8px; height: 8px; border-radius: 50%; margin-right: var(--space-3); flex-shrink: 0; background: var(--dot-color, var(--sidebar-text)); }

.main {
  grid-area: main;
  overflow: auto;
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.page-title {
  font-size: 18px;
  font-weight: 500;
  color: var(--color-text);
  padding: var(--space-4) var(--space-5) 0;
}

.icon-btn {
  background: transparent; border: none; color: var(--color-text-muted);
  width: 32px; height: 32px; border-radius: var(--radius-sm);
  display: inline-flex; align-items: center; justify-content: center; font-size: 16px;
}
.icon-btn:hover { background: var(--color-surface-alt); color: var(--color-text); }
.icon-btn svg { width: 18px; height: 18px; stroke: currentColor; }