chore(deps): bump pydantic-settings from 2.13.1 to 2.14.1 in /backend (#260)

Bumps [pydantic-settings](https://github.com/pydantic/pydantic-settings) from 2.13.1 to 2.14.1.
- [Release notes](https://github.com/pydantic/pydantic-settings/releases)
- [Commits](https://github.com/pydantic/pydantic-settings/compare/v2.13.1...v2.14.1)

---
updated-dependencies:
- dependency-name: pydantic-settings
  dependency-version: 2.14.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

backend/requirements.txt

@@ -2,7 +2,7 @@
 fastapi==0.135.3  # Updated: Fixed starlette DoS vulnerabilities (was 0.109.1); pulls in starlette>=1.0.0
 uvicorn[standard]==0.47.0
 pydantic==2.13.4
-pydantic-settings==2.13.1
+pydantic-settings==2.14.1
 
 # Database
 sqlalchemy==2.0.49  # Updated: Fixed Python 3.14 incompatibility with TypingOnly assertion (was 2.0.25)