Add option to override Celery worker images

[sg-c0de]

Summary

Since we have the option to configure multiple Celery worker sets, it is useful to be able to use different images for specific sets (for example, to include CUDA drivers). This adds the option to override the image for all Celery workers globally or on a per-set basis using Values.workers.celery.image and Values.workers.celery.sets[].image.

Changes

chart/templates/_helpers.yaml: Add airflow_worker_image, airflow_worker_image_pull_policy, and airflow_worker_image_for_migrations helpers, and patch the fullOverwrite helper to support image overrides.

chart/templates/workers/worker-deployment.yaml: Update image and imagePullPolicy references to use the new helper templates.

chart/values.yaml: Add new values to support the image overrides.

[boring-cyborg]

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[jscheffl]

Thanks, that option makes sense to me. Can you also please add some tests?

[potiuk]

@sg-c0de This PR has a few issues that need to be addressed before it can be reviewed — please see our Pull Request quality criteria.

Issues found:

• ⚠️ Missing Tests: The PR adds new Helm chart behavior (Celery worker image overrides via new helper templates and new values) but no Helm unit test files are included in the changeset. Per review guidelines, new public behavior requires tests covering success, failure, and edge cases. The Helm tests suite has a dedicated area for exactly this kind of templating logic.
• ⚠️ Description Does Not Match Code: The PR description states the new values are at Values.workers.celery.image and Values.workers.celery.sets[].image, but the _helpers.yaml patch references .Values.workers.image (not .Values.workers.celery.image). The values.yaml patch adds the image block inside the workers.celery section (after queue: "default"). This discrepancy between the described API surface and the actual template code is a code-correctness concern that warrants scrutiny from maintainers.

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