chore(deps): bump pydantic from 2.8.2 to 2.9.2 in /backend

Bumps [pydantic](https://github.com/pydantic/pydantic) from 2.8.2 to 2.9.2.
- [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/v2.8.2...v2.9.2)

---
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

@@ -1,6 +1,6 @@
 fastapi==0.111.0
 uvicorn[standard]==0.30.6
-pydantic==2.8.2
+pydantic==2.9.2
 python-multipart==0.0.9
 
 Flask==3.0.3