Bump asgiref from 3.8.1 to 3.9.1 in /back-end

Bumps [asgiref](https://github.com/django/asgiref) from 3.8.1 to 3.9.1.
- [Changelog](https://github.com/django/asgiref/blob/main/CHANGELOG.txt)
- [Commits](django/asgiref@3.8.1...3.9.1)

---
updated-dependencies:
- dependency-name: asgiref
  dependency-version: 3.9.1
  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

@@ -1,5 +1,5 @@
 anyio==4.9.0
-asgiref==3.8.1
+asgiref==3.9.1
 click==8.1.8
 contextlib2==21.6.0
 contextvars==2.4