chore: pin shas in Dockerfile

[zkoppert]

Pull Request

Proposed Changes

The base image of the Dockerfile has been updated to use a specific version of the python:3.12-slim image. This is done by referencing the image's SHA256 digest, which ensures that the same image is always used, increasing the reproducibility and security of the Docker build.

Readiness Checklist

Author/Contributor

• If documentation is needed for this change, has that been included in this pull request
• run make lint and fix any issues that you have introduced
• run make test and ensure you have test coverage for the lines you are introducing
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Reviewer

• Label as either fix, documentation, enhancement, infrastructure, maintenance or breaking