build(deps): bump pydantic-settings from 2.13.0 to 2.13.1 in /backend

Bumps [pydantic-settings](https://github.com/pydantic/pydantic-settings) from 2.13.0 to 2.13.1.
- [Release notes](https://github.com/pydantic/pydantic-settings/releases)
- [Commits](pydantic/pydantic-settings@v2.13.0...v2.13.1)

---
updated-dependencies:
- dependency-name: pydantic-settings
  dependency-version: 2.13.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]