fix(notification): add role=link and touch target to view-all button

- role="link" restores screen reader link semantics (Leonie blocker)
- min-h-[44px] px-1 meets WCAG 2.2 §2.5.8 and our 44×48px target size
- Comment in handleViewAll explains close-before-navigate ordering
- Tests updated to getByRole('link') + new call-order assertion

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

frontend/src/lib/notification/NotificationDropdown.svelte

@@ -14,7 +14,7 @@ type Props = {
 let { notifications, onMarkRead, onMarkAllRead, onClose }: Props = $props();
 
 function handleViewAll() {
-	onClose();
+	onClose(); // close first — avoids stale dropdown during navigation transition
 	goto('/aktivitaeten');
 }
 </script>
@@ -135,8 +135,9 @@ function handleViewAll() {
 	<div class="border-t border-line px-4 py-2">
 		<button
 			type="button"
+			role="link"
 			onclick={handleViewAll}
-			class="text-xs font-medium text-ink-2 transition-colors hover:text-ink"
+			class="min-h-[44px] px-1 text-xs font-medium text-ink-2 transition-colors hover:text-ink"
 		>
 			{m.chronik_view_all()}
 		</button>