feat: print queue size more often

cmd/bsky-users/main.go

···
 			if err != nil {
 				log.Printf("failed to begin transaction: %v\n", err)
 			}
+		}
 
+		if eventCount%2500 == 0 {
 			log.Printf("queue size: %d\n", queue.Size())
 		}
 	}