IONOS(build): clarify unable to create new PRs

[Copilot]

• Resolves: dont rebuild already built apps #127

Summary

Clarified with the PR author that I cannot create new pull requests as requested in the comment. The comment asked to "open a new pull request to apply changes based on the comments in [review thread 3459500637]", but this capability is outside my permissions.

The review thread contains 6 actionable feedback items:

1. Add exponential backoff to Artifactory upload retries (matching GitLab trigger pattern)
2. Disable original workflow triggers to prevent double execution
3. Clarify shallow clone comment regarding submodule SHA requirements
4. Add error handling for cache detection API failures
5. Remove redundant error checks (mixing set -e with manual validation)
6. Use unique heredoc delimiters to prevent JSON content collisions

TODO

• Await user confirmation to apply changes in current PR vs. creating new PR
• Apply review feedback if confirmed for this PR

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

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