Build aarch64 images for Python and Django base images

Description

Once !100 (merged) is merged, port django and Python base images to aarch64.

Further details

For local development, it is very convenient to have aarch64 images available for the Django and Python base images. Given th groundwork in !100 (merged), adding aarch64 support should be fairly straightforward.

Acceptance criteria

On Apple Silicon machines, pulling the django Docker image results in code running on aarch64 by default. This can be tested by running uname --machine inside the built images.

Links/references

• Groundwork can be seen in !100 (merged)