feat(t-paliad-105): hide Überfällig card at zero, alarm at >0

Überfällig is an emergency category — never a normal-state tile. Replace the
prior `.dashboard-card-quiet` dim-but-visible behavior with two states:

- overdue === 0 → card removed from the layout (`*-overdue-hidden`).
  The Dashboard summary grid and the Fristen summary cards now use
  `repeat(auto-fit, minmax(180px, 1fr))` so the row re-flows to 3 cards
  instead of leaving an empty 4th column.
- overdue > 0 → saturated red surface, white text, soft pulsing red ring
  via `paliad-alarm-pulse`. Honors `prefers-reduced-motion`. Dark theme
  uses a slightly lighter red so the alarm still pops on midnight.

Applied on both surfaces (`#dashboard-card-overdue` and the Fristen
`.frist-summary-card[data-status="overdue"]`).

frontend/src/client/dashboard.ts

@@ -133,10 +133,13 @@ function renderSummary(s: DeadlineSummary): void {
   setCount("dashboard-count-upcoming", s.upcoming);
   setCount("dashboard-count-completed", s.completed_this_week);
 
-  // Tone down the red card when there's nothing overdue — reduces alarm
-  // fatigue when the user has a clean slate.
+  // Überfällig is an emergency category — hide the card entirely on a clean
+  // slate (the .dashboard-summary-grid uses auto-fit so the row re-flows to
+  // 3 cards) and trip the alarm styling when there's anything overdue. See
+  // t-paliad-105.
   const overdueCard = document.getElementById("dashboard-card-overdue")!;
-  overdueCard.classList.toggle("dashboard-card-quiet", s.overdue === 0);
+  overdueCard.classList.toggle("dashboard-card-overdue-hidden", s.overdue === 0);
+  overdueCard.classList.toggle("dashboard-card-alarm", s.overdue > 0);
 }
 
 function renderMatters(s: MatterSummary): void {

frontend/src/client/deadlines.ts

@@ -95,11 +95,25 @@ async function loadSummary() {
     setCount("sum-week", sum.this_week);
     setCount("sum-upcoming", sum.upcoming);
     setCount("sum-completed", sum.completed);
+    applyOverdueState(sum.overdue);
   } catch {
     /* non-fatal */
   }
 }
 
+// Überfällig is an emergency category — hide the card on a clean slate (the
+// .frist-summary-cards grid uses auto-fit so the row re-flows to 3 cards) and
+// trip the alarm styling when there's anything overdue. Mirrors the Dashboard
+// logic in client/dashboard.ts. See t-paliad-105.
+function applyOverdueState(overdue: number) {
+  const card = document.querySelector<HTMLElement>(
+    '.frist-summary-card[data-status="overdue"]',
+  );
+  if (!card) return;
+  card.classList.toggle("frist-card-overdue-hidden", overdue === 0);
+  card.classList.toggle("frist-card-alarm", overdue > 0);
+}
+
 function setCount(id: string, n: number) {
   const el = document.getElementById(id);
   if (el) el.textContent = String(n);

frontend/src/styles/global.css

@@ -5115,8 +5115,11 @@ input[type="range"]::-moz-range-thumb {
 }
 
 .frist-summary-cards {
+    /* auto-fit so the row re-flows when a card is hidden (Überfällig is
+       hidden when the count is zero — see t-paliad-105). With explicit
+       `repeat(4, …)` a hidden card leaves an empty 4th column. */
     display: grid;
-    grid-template-columns: repeat(4, minmax(0, 1fr));
+    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
     gap: 0.75rem;
     margin: 0 0 1.5rem;
 }
@@ -5592,8 +5595,10 @@ input[type="range"]::-moz-range-thumb {
 }
 
 .dashboard-summary-grid {
+    /* auto-fit so the row re-flows when a card is hidden (Überfällig is
+       hidden when the count is zero — see t-paliad-105). */
     display: grid;
-    grid-template-columns: repeat(4, 1fr);
+    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
     gap: 1rem;
 }
 
@@ -5640,8 +5645,55 @@ input[type="range"]::-moz-range-thumb {
 .dashboard-card-done .dashboard-card-count  { color: var(--status-neutral-fg-2); }
 .dashboard-card-done                        { border-left: 3px solid var(--status-neutral-fg-2); }
 
-.dashboard-card-quiet .dashboard-card-count { color: var(--color-text-muted); }
-.dashboard-card-quiet { border-left-color: var(--color-border); }
+/* Überfällig alarm — see t-paliad-105.
+   When overdue > 0 the card flips from a calm border-left accent to a
+   saturated red surface with a soft pulsing ring. The matching JS toggles
+   `.dashboard-card-alarm` (Dashboard) and `.frist-card-alarm` (Fristen);
+   when overdue === 0 the card is hidden entirely instead of dimmed. */
+@keyframes paliad-alarm-pulse {
+    0%, 100% { box-shadow: 0 0 0 0   rgb(220 38 38 / 0.55); }
+    50%      { box-shadow: 0 0 0 10px rgb(220 38 38 / 0);    }
+}
+
+.dashboard-card-red.dashboard-card-alarm,
+.frist-summary-card.frist-card-overdue.frist-card-alarm {
+    background: #dc2626;
+    color: #ffffff;
+    border-color: #991b1b;
+    border-left-color: #7f1d1d;
+    animation: paliad-alarm-pulse 1.8s ease-in-out infinite;
+}
+
+.dashboard-card-red.dashboard-card-alarm .dashboard-card-count,
+.dashboard-card-red.dashboard-card-alarm .dashboard-card-label,
+.frist-summary-card.frist-card-overdue.frist-card-alarm .frist-summary-count,
+.frist-summary-card.frist-card-overdue.frist-card-alarm .frist-summary-label {
+    color: #ffffff;
+}
+
+.frist-summary-card.frist-card-overdue.frist-card-alarm .frist-summary-dot {
+    background: #ffffff;
+    opacity: 1;
+}
+
+.dashboard-card-overdue-hidden,
+.frist-card-overdue-hidden {
+    display: none;
+}
+
+@media (prefers-reduced-motion: reduce) {
+    .dashboard-card-red.dashboard-card-alarm,
+    .frist-summary-card.frist-card-overdue.frist-card-alarm {
+        animation: none;
+    }
+}
+
+:root[data-theme="dark"] .dashboard-card-red.dashboard-card-alarm,
+:root[data-theme="dark"] .frist-summary-card.frist-card-overdue.frist-card-alarm {
+    background: #ef4444;
+    border-color: #f87171;
+    border-left-color: #fca5a5;
+}
 
 /* --- Matter summary card --- */