feat: Update release process to skip Docker Hub login if credentials … - #6

…are missing and document repository secrets

What

Contract impact

• Endpoint(s):
• Status code changed: yes / no
• Response body changed: yes / no
• If either is "yes" -> a MINOR or MAJOR bump is required, plus a note in the release notes.

Checklist

• Targets develop (not master), unless this is a release or a hotfix
• dotnet test passes locally
• dotnet format --verify-no-changes is clean
• README updated if user-visible behaviour changed
• Validation contract table in README updated if the accepted/rejected set changed
• If this should ship: VERSION.md bumped and CHANGELOG.md has a section for that number

How to verify

curl -i -X POST http://localhost:5274/api/target \
  -H 'Content-Type: application/json' -d '{"key":"value"}'