feat(dist): Homebrew notify + AUR publish parity with CNA

[ulises-jeremias]

Summary

• Implement notify-homebrew.yml → repository_dispatch to Create-Python-App/homebrew-tap (seeded Formula + update-formula.yml)
• Implement publish-aur.yml → bump PKGBUILD from PyPI sdist, publish via github-actions-aur-publish, sync Create-Python-App/aur-package
• Expand smoke-distribution.yml (uvx / Homebrew / AUR / version cross-check)
• Document secrets and bootstrap in docs/DISTRIBUTION_SETUP.md; README install badges

Closes#155. Closes#156.

Test plan

• Confirm secrets on create-python-app: HOMEBREW_TAP_TOKEN, AUR_SSH_PRIVATE_KEY, AUR_REPO_TOKEN
• First-time AUR bootstrap (push PKGBUILD to aur.archlinux.org) per DISTRIBUTION_SETUP
• Manual: gh workflow run "Notify Homebrew tap" -f version=0.1.0
• Manual: gh workflow run "Publish to AUR" -f version=0.1.0
• brew tap Create-Python-App/tap && brew install create-awesome-python-app
• Smoke workflow passes after channels are live

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