fix: close pubsub connection on Subscribe error in CancelationPubSub

When redis.Subscribe succeeds but Receive() fails, the pubsub
connection was not being closed before returning the error. This caused
the subscriber goroutine to leak a Redis connection on each retry
iteration, eventually exhausting the connection pool.

Fixes #1095

internal/rdb/rdb.go

@@ -1488,6 +1488,7 @@ func (r *RDB) CancelationPubSub() (*redis.PubSub, error) {
 	pubsub := r.client.Subscribe(ctx, base.CancelChannel)
 	_, err := pubsub.Receive(ctx)
 	if err != nil {
+		pubsub.Close()
 		return nil, errors.E(op, errors.Unknown, fmt.Sprintf("redis pubsub receive error: %v", err))
 	}
 	return pubsub, nil