build(deps): Bump python-multipart from 0.0.22 to 0.0.31 in /backend

Bumps [python-multipart](https://github.com/Kludex/python-multipart) from 0.0.22 to 0.0.31.
- [Release notes](https://github.com/Kludex/python-multipart/releases)
- [Changelog](https://github.com/Kludex/python-multipart/blob/main/CHANGELOG.md)
- [Commits](Kludex/python-multipart@0.0.22...0.0.31)

---
updated-dependencies:
- dependency-name: python-multipart
  dependency-version: 0.0.31
  dependency-type: indirect
...

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Author: dependabot[bot]