use uv and ruff for dev tooling + add vscode settings and recommended extensions

[utkashd]

Hello, I noticed this repo's tooling is a bit dated, so I created this PR to modernize the dev tooling.

• switch to using uv for dependency management
• replace black + flake8 with ruff for linting and formatting
• add VS Code workspace settings, extensions

Callouts:

• in pyproject.toml I set exclude-newer = "7 days" to lessen supply chain risk
• it looks like this repository intentionally doesn't have a .vscode/. That seems odd, but maybe there's a good reason. If so, I'll remove the vscode changes
• all changes to code should only be formatting changes. The meat of this PR is in pyproject.toml, .vscode/, and the README

How to validate:

uv run ruff check   # "All checks pass!"
uv run ruff format  # "14 files left unchanged"
uv run pytest       # all tests should pass

[utkashd]

unused import; I assume this is safe to remove

[swansonk14]

This looks great, thank you so much @utkashd!

--JK