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/en.json

@@ -318,7 +318,11 @@
 	"comment_placeholder": "Write a comment…",
 	"comment_btn_post": "Send",
 	"comment_btn_reply": "Reply",
-	"comment_edited_label": "· edited",
+	"comment_edited_label": "(Edited)",
+	"comment_time_just_now": "just now",
+	"comment_time_minutes": "{count} minute(s) ago",
+	"comment_time_hours": "{count} hour(s) ago",
+	"comment_time_days": "{count} day(s) ago",
 	"comment_panel_title": "Comments",
 	"comment_panel_close": "Close",
 	"doc_panel_tab_metadata": "Metadata",