Bump anyio from 4.12.1 to 4.13.0 in /back-end

Bumps [anyio](https://github.com/agronholm/anyio) from 4.12.1 to 4.13.0.
- [Release notes](https://github.com/agronholm/anyio/releases)
- [Commits](agronholm/anyio@4.12.1...4.13.0)

---
updated-dependencies:
- dependency-name: anyio
  dependency-version: 4.13.0
  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

@@ -1,4 +1,4 @@
-anyio==4.12.1
+anyio==4.13.0
 asgiref==3.11.1
 click==8.3.1
 contextlib2==21.6.0