automagic template - docker container build occurs when it shouldnt

the job definition docker/build.gitlab-ci.yaml does no checks to ensure there is a docker file, so the job is automagically created when it shouldn't be.

see https://gitlab.com/nofusscomputing/ops/-/pipelines/880798193 for more details

🚧 Tasks

• add a check to the job definition to ensure that a dockerfile exists as the pre-req for creating the job