feat: add container cleanup cronjob

[rbtr]

Prunes any non-release image tags from the container registry daily at 00:00Z. "non-release" tags include:

• SemVer prelease such as :v1.2.3-6f5089b0 suffixed tags
• bare commit tags such as :6f5089b0

"release" tags include only bare SemVer such as :v1.2.3, specifically matching the RegEx "^v(0|[1-9]\\d*)\\.(0|[1-9]\\d*)\\.(0|[1-9]\\d*)$", and will be skipped