chore(deps): bump pydantic from 2.7.1 to 2.8.2 in /backend

Bumps [pydantic](https://github.com/pydantic/pydantic) from 2.7.1 to 2.8.2.
- [Release notes](https://github.com/pydantic/pydantic/releases)
- [Changelog](https://github.com/pydantic/pydantic/blob/main/HISTORY.md)
- [Commits](https://github.com/pydantic/pydantic/compare/v2.7.1...v2.8.2

)

---
updated-dependencies:
- dependency-name: pydantic
  dependency-type: direct:production
  update-type: version-update:semver-minor
...
Signed-off-by: dependabot[bot] <support@github.com>

backend/requirements.txt

 fastapi==0.111.0
 uvicorn[standard]==0.22.0
-pydantic==2.7.1
+pydantic==2.8.2
 python-multipart==0.0.9
 
 Flask==3.0.3