docs: add UI testing guide for QA in readme/USAGE.md

- Add comprehensive USAGE.md with curl examples for all 12 CR API endpoints
- Update DESCRIPTION.md to match actual code ($types endpoints, scopes, auto_install)
- Expand test coverage to 95%+ with ~43 new service and API tests
- Regenerate README.rst via oca-gen-addon-readme

Author: gonzalesedwin1123