Bump fastapi from 0.120.1 to 0.121.0 in /back-end

Bumps [fastapi](https://github.com/fastapi/fastapi) from 0.120.1 to 0.121.0.
- [Release notes](https://github.com/fastapi/fastapi/releases)
- [Commits](fastapi/fastapi@0.120.1...0.121.0)

---
updated-dependencies:
- dependency-name: fastapi
  dependency-version: 0.121.0
  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

@@ -3,7 +3,7 @@ asgiref==3.10.0
 click==8.1.8
 contextlib2==21.6.0
 contextvars==2.4
-fastapi==0.120.1
+fastapi==0.121.0
 h11==0.16.0
 idna==3.11
 immutables==0.21