fix: replace CSS keyframe highlight with direct style pulse for reliability

CSS animation was interfering with stagger animation on cards.
Now uses setInterval-based box-shadow pulse with computed primary
color from CSS variables. Pulses glow on/off every 400ms for 2.5s,
then fades out via transition.

frontend/src/app.css

@@ -184,12 +184,7 @@ a:focus-visible {
 	font-family: var(--font-mono);
 }
 
-/* Card highlight for cross-entity navigation */
-@keyframes cardHighlight {
-	0%, 100% { box-shadow: none; }
-	25%, 75% { box-shadow: 0 0 0 3px var(--color-primary), 0 0 20px color-mix(in srgb, var(--color-primary) 30%, transparent); }
-}
-
+/* Card highlight dim overlay for cross-entity navigation */
 .nav-dim-overlay {
 	position: fixed;
 	inset: 0;

frontend/src/lib/highlight.ts

@@ -2,21 +2,19 @@
  * Card highlight system for cross-entity navigation.
  *
  * When navigating via CrossLink, the target entity ID is passed as ?highlight=<id>.
- * The destination page calls highlightFromUrl() on mount, which:
+ * The destination page calls highlightFromUrl() after data loads, which:
  * 1. Shows a dim overlay behind everything
  * 2. Finds the card with [data-entity-id="<id>"]
  * 3. Scrolls to it smoothly
- * 4. Applies a pulsing box-shadow animation
- * 5. Cleans up after 2 seconds
- *
- * If the card isn't in the DOM yet (data still loading), a MutationObserver
- * waits up to 5 seconds for it to appear.
+ * 4. Applies a pulsing glow via direct style manipulation
+ * 5. Cleans up after 2.5 seconds
  */
 
-const HIGHLIGHT_DURATION = 2000;
+const HIGHLIGHT_DURATION = 2500;
+const PULSE_INTERVAL = 400;
 const WAIT_TIMEOUT = 5000;
 
-/** Show dim overlay, find card, scroll & highlight. Call from onMount or $effect. */
+/** Show dim overlay, find card, scroll & highlight. Call after data loads. */
 export function highlightFromUrl(): void {
 	if (typeof window === 'undefined') return;
 	const params = new URLSearchParams(window.location.search);
@@ -32,7 +30,8 @@ export function highlightFromUrl(): void {
 	// Try to find the card now, or wait for it
 	const card = document.querySelector(`[data-entity-id="${id}"]`);
 	if (card) {
-		_highlightCard(card as HTMLElement);
+		// Small delay for layout to settle after loaded=true
+		setTimeout(() => _highlightCard(card as HTMLElement), 100);
 	} else {
 		_waitForCard(id);
 	}
@@ -45,28 +44,52 @@ function _highlightCard(card: HTMLElement): void {
 	// Scroll to card
 	card.scrollIntoView({ behavior: 'smooth', block: 'center' });
 
-	// Kill the stagger animation first so it won't replay on cleanup
-	card.style.animation = 'none';
-	// Force reflow to commit the "none"
-	void card.offsetHeight;
-	// Now set the highlight animation + z-index above overlay
-	card.style.animation = 'cardHighlight 2s ease-in-out';
+	// Save original styles
+	const origBoxShadow = card.style.boxShadow;
+	const origZIndex = card.style.zIndex;
+	const origPosition = card.style.position;
+	const origBorderColor = card.style.borderColor;
+
+	// Elevate above overlay
 	card.style.position = 'relative';
 	card.style.zIndex = '11';
 
-	// Cleanup after duration
+	// Get primary color from CSS variable
+	const primary = getComputedStyle(document.documentElement)
+		.getPropertyValue('--color-primary').trim();
+
+	// Pulse effect via interval
+	let on = true;
+	const glowOn = `0 0 0 3px ${primary}, 0 0 24px ${primary}60`;
+	const glowOff = `0 0 0 2px ${primary}80`;
+
+	card.style.boxShadow = glowOn;
+	card.style.borderColor = primary;
+
+	const pulseTimer = setInterval(() => {
+		on = !on;
+		card.style.boxShadow = on ? glowOn : glowOff;
+	}, PULSE_INTERVAL);
+
+	// Cleanup
 	setTimeout(() => {
-		// Set animation to "none" to prevent stagger replay, then remove inline overrides
-		card.style.animation = 'none';
-		card.style.removeProperty('position');
-		card.style.removeProperty('z-index');
-		overlay.classList.remove('active');
-		setTimeout(() => overlay.remove(), 300);
+		clearInterval(pulseTimer);
+		// Fade out: transition the box-shadow away
+		card.style.transition = 'box-shadow 0.3s ease, border-color 0.3s ease';
+		card.style.boxShadow = origBoxShadow;
+		card.style.borderColor = origBorderColor;
+
+		setTimeout(() => {
+			card.style.position = origPosition;
+			card.style.zIndex = origZIndex;
+			card.style.removeProperty('transition');
+			overlay.classList.remove('active');
+			setTimeout(() => overlay.remove(), 300);
+		}, 300);
 	}, HIGHLIGHT_DURATION);
 }
 
 function _showDimOverlay(): HTMLElement {
-	// Reuse existing overlay if present
 	let overlay = document.querySelector('.nav-dim-overlay') as HTMLElement | null;
 	if (!overlay) {
 		overlay = document.createElement('div');
@@ -86,8 +109,7 @@ function _waitForCard(id: string): void {
 		const card = document.querySelector(`[data-entity-id="${id}"]`);
 		if (card) {
 			observer.disconnect();
-			// Small delay for layout to settle
-			requestAnimationFrame(() => _highlightCard(card as HTMLElement));
+			setTimeout(() => _highlightCard(card as HTMLElement), 100);
 			return;
 		}
 		if (Date.now() - start > WAIT_TIMEOUT) {
@@ -96,7 +118,5 @@ function _waitForCard(id: string): void {
 	});
 
 	observer.observe(document.body, { childList: true, subtree: true });
-
-	// Safety timeout
 	setTimeout(() => observer.disconnect(), WAIT_TIMEOUT);
 }