Problem

The CONTRIBUTING.md file currently references black as the recommended code formatter and displays a "Codestyle: black" badge. However, the project configuration (pyproject.toml and .pre-commit-config.yaml) shows that the project has migrated to ruff for both linting and formatting.

Goal

Update the documentation to accurately reflect the current tooling chain to avoid confusion for new contributors.

Proposed Changes

• Replace text references recommending black with ruff.
• Replace the black badge with the ruff badge in the "Testing and Code Standards" section.
• Update the reference links at the bottom of the file to point to the ruff repository.