Add make actions to replicate CI/CD functionalities

[todor-ivanov]

Summary

Implements the manual Makefile-driven release flow requested in #153.

This PR adds explicit Make targets for maintainer-controlled image publication and deployment actions that were previously only described in GitHub Actions, including:

• image upload/publication to registry.cern.ch/cmsweb/dbs2go;
• stable tag handling for final releases;
• no-Oracle image upload variants;
• imagebot-based k8s deployment updates;
• README documentation for the manual release/upload/deploy procedure.

The intended release flow becomes explicit and locally controlled:

git tag <release-tag>
make upload TAG=<release-tag>
make k8deploy TAG=<release-tag> IMAGEBOT_URL=<imagebot-url>

This addresses the Makefile-side requirements from #153 by making the privileged release operations manually executable through make.

Closes #153.

[vkuznet]

I suggest to separate docker build from push actions.

[vkuznet]

Todor, I suggest to separate docker build from docker push since here you don't even check if build was successful. Moreover, sometimes we may prefer to build local image but do not upload it yet to registry.