CONTRIBUTING.md adapted for uv / Typer / PyPI

[ulises-jeremias]

Summary

Contributor guide with local uv workflow.

CNA mapping

CNA: CONTRIBUTING.md.

Acceptance criteria

• Clone/sync/test/lint instructions
• PR expectations + conventional commits
• Points to Code of Conduct

Blocked by

none

Blocks

none

Reference

Parity matrix (workspace): knowledge/create-python-app-parity-matrix.md
Reference repo: https://github.com/Create-Node-App/create-node-app

Parent epic

#8