/// Formats a past [DateTime] as a short relative string ("2h ago",
/// "5d ago") for activity feeds and stat-tile captions — full timestamps
/// belong in tables (as [MonoText]), not here.
String formatRelative(DateTime dateTime) {
  final diff = DateTime.now().difference(dateTime);
  if (diff.inSeconds < 45) return 'just now';
  if (diff.inMinutes < 60) return '${diff.inMinutes}m ago';
  if (diff.inHours < 24) return '${diff.inHours}h ago';
  if (diff.inDays < 7) return '${diff.inDays}d ago';
  if (diff.inDays < 30) return '${(diff.inDays / 7).floor()}w ago';
  return '${(diff.inDays / 30).floor()}mo ago';
}