Bump pytest from 8.3.5 to 8.4.0 in /back-end

Bumps [pytest](https://github.com/pytest-dev/pytest) from 8.3.5 to 8.4.0.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@8.3.5...8.4.0)

---
updated-dependencies:
- dependency-name: pytest
  dependency-version: 8.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

back-end/requirements.txt

@@ -15,7 +15,7 @@ sniffio==1.3.1
 starlette==0.46.2
 typing_extensions==4.13.2
 uvicorn==0.34.2
-pytest==8.3.5
+pytest==8.4.0
 pytest-cov==6.1.1
 mysql-connector==2.2.9
 mysql-connector-python==9.3.0