[Task](ci): improve Concourse Deployment and Helm Chart References for Greenhouse to use stable Images and Keppel

[ArtieReus]

Task Description
Enhance the existing Concourse deployment pipeline to tag production images of Greenhouse with a stable tag, update Helm charts to reference this tag, and ensure pipeline compatibility with stable images and images digest for ccloud.

Sub-tasks

1. Tag Production Images

• Extend the current Concourse deployment pipeline to tag the production Greenhouse images with stable.

2. Update Helm Chart References

• Modify the Helm charts to reference the stable tag.
• This change will ensure that chart releases use the latest stable images without relying on an outdated image digest.

3. Adjust Pipeline for QA and Production Compatibility

• Update the Concourse pipeline to continue using image digests for continuous deployment to the QA environment.

4. Use Keppel for internal deployment

Related Issues
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