[Proposal] Support uv for package management

[hijohnnylin]

Proposal

We should support uv (instead of or replacing? poetry).

Motivation

uv is:

1. Faster
2. Better supported (subjective somewhat)
3. Does not seem to be a passing fad

Pitch

• Updating project files as necessary to port to uv
• Update README for uv
• Test a least 1 library that depends on SAELens to ensure everything works the same (even if that package uses poetry - maybe SAEBench?)

Alternatives

People use uv but without us officially supporting it.

• I have checked that there is no similar issue in the repo (required)

I searched for "uv" in open issues and found nothing