Set retention rules in the harbor repository

Reported in https://gitlab.cta-observatory.org/cta-computing/suss/long-term-and-mid-term-scheduler/mts/-/issues/19

2. High disk usage: (I think) we push an image for every branch into the harbour and nothing is being deleted.

We need to set some retention rules to clean up regularly the harbor repository, keeping for some time the dev versions and indefinitely the tagged ones.

Right now only applicable to alma-stars-image repository as MTS repository is currently not uploading images to the harbor. However, it is a wider problem affecting all repositories.