fix(docker): missing variable in development environement

.env.dev

@@ -6,6 +6,7 @@ DESECSTACK_NS=ns1.example.com
 DESECSTACK_IPV4_REAR_PREFIX16=172.16
 DESECSTACK_IPV6_SUBNET=fda8:7213:9e5e:1::/80
 DESECSTACK_IPV6_ADDRESS=fda8:7213:9e5e:1::0642:ac10:0080
+DESECSTACK_PORT_XFR=53
 
 # certificates
 DESECSTACK_WWW_CERTS=./certs