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/messages/en.json

@@ -758,7 +758,7 @@
 
 	"dropzone_release": "Release to upload",
 
-	"chronik_page_title": "Chronicle",
+	"chronik_page_title": "Activity",
 	"chronik_for_you_caption": "For you",
 	"chronik_for_you_count": "{count} new",
 	"chronik_mark_read_aria": "Mark as read",
@@ -790,10 +790,10 @@
 	"chronik_empty_first_run_body": "As soon as someone in the family uploads or transcribes a document, the activity will show up here.",
 	"chronik_empty_filter_title": "Nothing in this view",
 	"chronik_empty_filter_body": "There are no entries for this filter.",
-	"chronik_error_title": "The chronicle could not be loaded.",
+	"chronik_error_title": "Activity could not be loaded.",
 	"chronik_error_retry": "Try again",
 	"chronik_load_more": "Load more",
 	"chronik_loading": "Loading …",
 	"chronik_load_more_announcement": "{count} more entries loaded",
-	"chronik_view_all": "Open chronicle →"
+	"chronik_view_all": "All activity →"
 }