build: uplift Python kata baseline

[megabyde]

Summary

• require Python 3.11 and use the locked pytest 9.1.1 and Ruff 0.16.1 toolchain
• replace Poetry, YAPF, and Replit-only setup with PEP 621 metadata, uv, Ruff, and three-platform CI
• standardize Make targets, ownership, weekly dependency updates, and reproducible setup while preserving the Roman Numerals exercises, entry point, run target, and tests

Verification

• default make and make help
• UV_CACHE_DIR=/tmp/roman-numerals-python-kata-uv-cache uv lock --check
• UV_CACHE_DIR=/tmp/roman-numerals-python-kata-uv-cache make format-check
• UV_CACHE_DIR=/tmp/roman-numerals-python-kata-uv-cache make test; UV_CACHE_DIR=/tmp/roman-numerals-python-kata-uv-cache make run
• parsed workflow and Dependabot YAML
• make clean cache-removal and preservation checks
• git diff --check origin/main...HEAD

Required checks

• lint
• test (ubuntu-latest)
• test (macos-latest)
• test (windows-latest)