Chore/pre commit hooks 88

[suhaslord]

Summary

Adds pre-commit hooks to make the local development checks match the repo’s existing CI more closely.

Changes

• added .pre-commit-config.yaml
  • runs the critical flake8 checks before commits
  • runs mypy before commits
  • runs the full pytest suite before pushes
• added CONTRIBUTING.md
  • basic Poetry setup
  • how to install/use pre-commit
  • commands for running the checks manually

This keeps the setup pretty lightweight while catching the same kinds of issues earlier, before they reach CI.

Closes #88

[chuckwondo]

@suhaslord, I rebased your branch on main because I merged some bot bumps, so you'll need to pull those changes on your branch, but since I rebased it, I strongly recommend you configure your git client as follows, which will prevent git pull from failing to pull the rebased branch:

git config set --global pull.rebase true