build(deps-dev): bump types-protobuf in /backend

Bumps [types-protobuf](https://github.com/python/typeshed) from 5.28.3.20241030 to 5.29.1.20241207.
- [Commits](https://github.com/python/typeshed/commits)

---
updated-dependencies:
- dependency-name: types-protobuf
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>