ci(dist): stabilize AUR publish workflow (currently failing)

[ulises-jeremias]

Problem

publish-aur.yml has multiple recent failures (timeouts/504 to AUR). The AUR package create-awesome-python-app exists at 0.1.0-1, but automation is not trustworthy for the next release.

Acceptance criteria

• Identify root cause (AUR SSH/RPC flake, secrets, PKGBUILD path, rate limit)
• Add retries/backoff or clearer failure messaging where appropriate
• Document operator steps in docs/DISTRIBUTION_SETUP.md if secrets/env need fixes
• One successful workflow_dispatch publish (or dry-run equivalent) recorded here
• Next tagged release updates AUR without manual rescue

References

• Related: feat(dist): AUR publish workflow + aur-package mirror #156, AUR publish tracking + workflow #60, [Epic 8] Distribution — PyPI, Docker, AUR, Homebrew #9
• Repo: Create-Python-App/aur-package