Updates UI: removes elkjs, updates backend deps

[skrawcz]

Changes

Removes elkjs and adds dagre

Need to test this more -- but basic graphs work.

Updates backend to use UV and updates to use 3.9

So python 3.8 is gone. Updates to use python 3.9
Updates deps and to use uv for reproducible builds.

How I tested this

• locally

Notes

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.

[zilto]

For reference, there are ways to optimize the Docker build process such that it uses the host's local uv cache when building Python dependencies inside the container. This can lead to significant speed improvement in dev

example: https://github.com/astral-sh/uv-docker-example/blob/main/multistage.Dockerfile

[zilto]

I see that Dockerfile.backend and Dockerfile.backend-prod already existed, but it seems they were identical except the additional line 15 (origin) in backend-prod?

I have a few questions:

• why are two files needed?
• why use the frozen requirements-locked.txt in backend-prod? This just seems like a weaker uv.lock. Are there any particular trade-offs?
• In backend-prod, the line COPY . /code/ appears twice (line 15 and line 20 in origin). Is this intended?