feat: card highlight system for cross-entity navigation

When clicking a CrossLink, the target entity ID is passed as
?highlight=<id> in the URL. The destination page:
1. Shows a semi-transparent dim overlay (z-index: 10)
2. Finds the card with data-entity-id matching the ID
3. Scrolls to it smoothly (block: center)
4. Applies a pulsing primary-color box-shadow animation (z-index: 11)
5. Cleans up overlay + animation after 2 seconds

If the card isn't in DOM yet (data still loading), a MutationObserver
waits up to 5 seconds for it to appear.

Changes:
- New highlight.ts utility with highlightFromUrl(), MutationObserver,
  dim overlay management
- Card component accepts entityId prop → data-entity-id attribute
- CrossLink accepts entityId prop → appends ?highlight=<id> to href
- All 9 entity pages: Card elements have entityId, highlightFromUrl()
  called after data loads
- CSS: cardHighlight keyframe animation + nav-dim-overlay styles

frontend/src/routes/tracking-configs/+page.svelte

@@ -14,6 +14,7 @@
 	import Hint from '$lib/components/Hint.svelte';
 	import IconButton from '$lib/components/IconButton.svelte';
 	import { snackSuccess, snackError } from '$lib/stores/snackbar.svelte';
+	import { highlightFromUrl } from '$lib/highlight';
 	import type { TrackingConfig } from '$lib/types';
 
 	let configs = $derived(trackingConfigsCache.items);
@@ -43,7 +44,7 @@
 	async function load() {
 		try { await trackingConfigsCache.fetch(true); }
 		catch (err: any) { error = err.message || t('common.loadError'); snackError(error); }
-		finally { loaded = true; }
+		finally { loaded = true; highlightFromUrl(); }
 	}
 
 	function openNew() { form = defaultForm(); editing = null; showForm = true; }
@@ -208,7 +209,7 @@
 {:else}
 	<div class="space-y-3 stagger-children">
 		{#each configs as config}
-			<Card hover>
+			<Card hover entityId={config.id}>
 				<div class="flex items-center justify-between">
 					<div>
 						<div class="flex items-center gap-2">