Use proper BASE_IMAGE in contributed recipes for forks

[mathbunnyru]

Describe your changes

Issue ticket if applicable

Checklist (especially for first-time contributors)

• I have performed a self-review of my code
• If it is a core feature, I have added thorough tests
• I will try not to use force-push to make the review process easier for reviewers
• I have updated the documentation for significant changes

[mathbunnyru]

What happened:

1. I pinned libxml2 in both jupyter/docker-stacks and my fork (almost simultaneously).
2. My fork started running docker.yml workflow, which then runs contributed-recipes.yml workflow
3. Instead of using fork built images, contributed recipes in my fork used images pushed to the jupyter registry (images with libxml2 pin were not yet pushed, so previous images were used)
4. I got a failure: https://github.com/mathbunnyru/docker-stacks/actions/runs/14419023194/job/40439441899

[mathbunnyru]

I don't think it's possible to write a ternary here, but if someone knows how do it, it would be great