fix(ci): wait for PyPI simple index before Docker build

[ulises-jeremias]

Summary

publish-docker.yml waits on the JSON API (/pypi/{pkg}/{ver}/json) before building. That endpoint can return 200 while the simple index pip uses inside the Docker build is still stale, causing:

ERROR: No matching distribution found for create-awesome-python-app==X.Y.Z

Seen on the 0.2.5 release: https://github.com/Create-Python-App/create-python-app/actions/runs/29651389715

Acceptance

• Wait step also verifies the version appears on https://pypi.org/simple/{package}/ (or equivalent pip-visible check)
• Manual workflow_dispatch for an already-published version still works
• Document briefly why both checks exist

Notes

Immediate mitigation for 0.2.5: re-run Publish Docker image via workflow_dispatch after simple-index propagation.