fix(person-mention): name the hover-card region and announce its busy state

Leonie FINDING-02/03 + Elicit NFR concern + Sara #4: role="region" with no
aria-label is an axe-core warning, and the pulsing-bars skeleton carries no
semantics for SR clients.

- Add aria-label to the region root: person displayName when loaded,
  localised "Lade Person…" while loading. Region always has a name.
- Add aria-busy="true" while loading; cleared on loaded/error so the
  state change is announced via aria-live="polite".
- Add role="status" + aria-label on the skeleton so SR clients hear
  "Lade Person" rather than three silent <div>s.
- New Paraglide key person_mention_loading in de/en/es.

Five new tests pin: aria-busy true while loading, aria-busy unset/false
when loaded, aria-label is displayName when loaded, aria-label is the
loading label while loading.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/PersonHoverCard.svelte

@@ -41,6 +41,17 @@ const notesExcerpt = $derived.by(() => {
 	if (notes.length <= NOTES_MAX) return notes;
 	return notes.slice(0, NOTES_MAX) + '…';
 });
+
+// Accessible name for the region landmark — required by WCAG 1.3.1.
+// Falls back to a localised loading label so axe-core never sees an unnamed
+// region (Leonie FINDING-02 / Elicit NFR concern).
+const ariaLabel = $derived(
+	state.status === 'loaded' ? state.person.displayName : m.person_mention_loading()
+);
+
+// aria-busy="true" while loading so SR clients know the region's contents
+// will change. Cleared on loaded/error so the new content is announced.
+const ariaBusy = $derived(state.status === 'loading');
 </script>
 
 <div
@@ -49,12 +60,19 @@ const notesExcerpt = $derived.by(() => {
 	id={cardId}
 	role="region"
 	aria-live="polite"
+	aria-label={ariaLabel}
+	aria-busy={ariaBusy ? 'true' : undefined}
 	style:position="absolute"
 	style:top={`${position.top}px`}
 	style:left={`${position.left}px`}
 >
 	{#if state.status === 'loading'}
-		<div data-testid="person-hover-card-skeleton" class="skeleton">
+		<div
+			data-testid="person-hover-card-skeleton"
+			class="skeleton"
+			role="status"
+			aria-label={m.person_mention_loading()}
+		>
 			<div class="bar"></div>
 			<div class="bar"></div>
 			<div class="bar"></div>