fix: keep DM participant rows when a user leaves the chat group

The participant sync and the non-member prune now remove only ogólny's
rows. A user taken out of studenci, even briefly, keeps their DMs (the
live membership check denies access while they are out) and gets them
back when re-added, instead of losing them for good.

console/chat_sync.go

@@ -49,7 +49,7 @@ func ChatSyncCommand(withDB func(ctx context.Context, fn func(*gorm.DB) error) e
 				} else {
 					out.Printf("ogólny participants added: %d\n", added)
 				}
-				out.Printf("participant rows removed: %d\n", removed)
+				out.Printf("ogólny participants removed: %d\n", removed)
 				out.Printf("handles assigned: %d\n", handles)
 				out.Success(chatSyncName + ": chat group " + group + " synced")
 				return nil