Add pre-commit configuration and update README for backend development

[yoland68]

Add pre-commit configuration and backend development docs

Changes

• Added .pre-commit-config.yaml to standardize code quality checks
• Updated README with backend development setup instructions

Details

Pre-commit Configuration

Added pre-commit hooks for:

• Ruff for Python linting and code style checks
• Pytest for automated testing

Documentation Updates

Added a new "ComfyUI Backend Development" section to the README that includes:

• Environment setup instructions for pre-commit
• Guidelines for reporting backend-specific issues

Why

These changes will help:

• Maintain consistent code quality through automated checks
• Make it easier for new contributors to set up their development environment
• Direct backend-related issues to the appropriate repository

Testing

• Verified pre-commit hooks run successfully
• Confirmed README changes render correctly on GitHub