Migrate copyright and BCR ownership to MBO Works

[helly25]

Summary

• attribute source files to M. Boerger and the MBO Works authors
• publish BCR changes through mboworks/bazel-central-registry
• use M. Boerger as the informational BCR maintainer name while retaining the helly25 approval identity

Validation

• git diff --check
• pre-commit run --all-files
• bazel test //...