Update github ci/cd to build `admin` service and store image

[akdasa]

We must build a vidya-admin image every time sources at modules/services/admin change (on the main branch, after PR is merged, or commit to the main)

Acceptance Criteria

• When I commit to the main (with changes in vidya-admin) Then new vidya-admin image builds
• When I commit to the main (without changes in vidya-admin) Then do nothing

Additional Resources

How to run GitHub Actions workflow only if the pushed files are in a specific folder