transfer compute_backend functionality to a celery worker

[jerodway]

          In terms of slimming down, we can just update the celeryworker.dockerfile to use your pypy configuration.  And then move that forcegraph crud stuff to the celery worker.  That way we get the pypy speed up along with the full async benefits from FastAPI but only have to worry about 1 API/docs/etc.

Originally posted by @0mdb in #65 (comment)

Seeing as it works as-is, this busywork is very low priority.