feat(chronik): align layout to grouped card pattern; fix duplicate rollup count

- ChronikTimeline: date buckets now render as bordered cards with muted
  header (border-line / bg-surface / shadow-sm) and divide-y row
  separators, matching the DocumentList card pattern
- ChronikRow: remove rounded-sm (card handles clipping), hover:bg-canvas
  → hover:bg-muted/50; restore rollup count badge after doc title
- Messages (de/en/es): remove embedded {count} from all four rollup verb
  strings so the badge is the single source of truth, consistent with
  DashboardActivityFeed

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

frontend/messages/de.json

@@ -776,13 +776,13 @@
 	"chronik_day_this_week": "Diese Woche",
 	"chronik_day_older": "Älter",
 	"chronik_singleton_text_saved": "{actor} transkribierte einen Block in {doc}",
-	"chronik_rollup_text_saved": "{actor} transkribierte {count} Blöcke in {doc}",
+	"chronik_rollup_text_saved": "{actor} transkribierte {doc}",
 	"chronik_singleton_uploaded": "{actor} lud {doc} hoch",
-	"chronik_rollup_uploaded": "{actor} lud {count} Dokumente hoch",
+	"chronik_rollup_uploaded": "{actor} lud Dokumente hoch",
 	"chronik_singleton_reviewed": "{actor} überprüfte einen Block in {doc}",
-	"chronik_rollup_reviewed": "{actor} überprüfte {count} Blöcke in {doc}",
+	"chronik_rollup_reviewed": "{actor} überprüfte {doc}",
 	"chronik_singleton_annotated": "{actor} annotierte {doc}",
-	"chronik_rollup_annotated": "{actor} annotierte {doc} {count}×",
+	"chronik_rollup_annotated": "{actor} annotierte {doc}",
 	"chronik_comment_added": "{actor} kommentierte {doc}",
 	"chronik_mention_created": "{actor} erwähnte dich in {doc}",
 	"chronik_reply_received": "{actor} antwortete dir in {doc}",