Use Black and Ruff for formatting/linting

Use Black for formatting and Ruff for linting:
- Black: Uncompromising code formatter (no configuration debates)
- Ruff: Extremely fast linter (replaces flake8, isort, pylint)

```toml
# pyproject.toml
[tool.black]
line-length = 88

[tool.ruff]
line-length = 88
select = ["E", "F", "I", "N", "W", "UP"]
```

Run both in CI and pre-commit hooks.