fix(i18n): translate comment timestamps and edited label

Replace hardcoded German strings in CommentThread.timeAgo() with
Paraglide i18n keys: comment_time_just_now, comment_time_minutes,
comment_time_hours, comment_time_days.

Update comment_edited_label from "· bearbeitet" to "(Bearbeitet)"
for the new single-timestamp design. All three languages: de/en/es.

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

frontend/messages/de.json

@@ -318,7 +318,11 @@
 	"comment_placeholder": "Kommentar schreiben…",
 	"comment_btn_post": "Senden",
 	"comment_btn_reply": "Antworten",
-	"comment_edited_label": "· bearbeitet",
+	"comment_edited_label": "(Bearbeitet)",
+	"comment_time_just_now": "gerade eben",
+	"comment_time_minutes": "vor {count} Minute(n)",
+	"comment_time_hours": "vor {count} Stunde(n)",
+	"comment_time_days": "vor {count} Tag(en)",
 	"comment_panel_title": "Kommentare",
 	"comment_panel_close": "Schließen",
 	"doc_panel_tab_metadata": "Metadaten",