Bump tomlkit from 0.12.5 to 0.13.0 in /backend

Bumps [tomlkit](https://github.com/sdispater/tomlkit) from 0.12.5 to 0.13.0.
- [Release notes](https://github.com/sdispater/tomlkit/releases)
- [Changelog](https://github.com/python-poetry/tomlkit/blob/master/CHANGELOG.md)
- [Commits](python-poetry/tomlkit@0.12.5...0.13.0)

---
updated-dependencies:
- dependency-name: tomlkit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/requirements.txt

@@ -19,5 +19,5 @@ pluggy==1.5.0
 pylint==3.1.1
 pytest==8.2.2
 six==1.16.0
-tomlkit==0.12.5
+tomlkit==0.13.0
 Werkzeug==3.0.3