feat(chronik): rename route and heading to Aktivitäten

/chronik → /aktivitaeten; heading updated in all three locales.
Component folder (lib/components/chronik/) stays unchanged — internal
implementation detail, not user-facing.

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

frontend/src/routes/profile/+page.svelte

@@ -102,7 +102,10 @@ const hasEmail = $derived(!!data.user?.email);
 		</form>
 
 		<div class="mt-4 border-t border-line pt-4">
-			<a href="/chronik" class="text-sm font-medium text-ink-2 transition-colors hover:text-ink">
+			<a
+				href="/aktivitaeten"
+				class="text-sm font-medium text-ink-2 transition-colors hover:text-ink"
+			>
 				{m.notification_history_view_link()}
 			</a>
 		</div>