Bump pytest from 8.4.2 to 9.0.0 in /back-end

Bumps [pytest](https://github.com/pytest-dev/pytest) from 8.4.2 to 9.0.0.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@8.4.2...9.0.0)

---
updated-dependencies:
- dependency-name: pytest
  dependency-version: 9.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

back-end/requirements.txt

@@ -15,7 +15,7 @@ sniffio==1.3.1
 starlette==0.48.0
 typing_extensions==4.15.0
 uvicorn==0.38.0
-pytest==8.4.2
+pytest==9.0.0
 pytest-cov==7.0.0
 mysql-connector==2.2.9
 mysql-connector-python==9.5.0