Bump django-timezone-field from 7.0 to 7.1 in /backend

Bumps [django-timezone-field](https://github.com/mfogel/django-timezone-field) from 7.0 to 7.1.
- [Commits](mfogel/django-timezone-field@7.0...7.1)

---
updated-dependencies:
- dependency-name: django-timezone-field
  dependency-version: '7.1'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

backend/pyproject.toml

@@ -47,7 +47,7 @@ dependencies = [
     "django==5.1.4",
     "django-environ==0.10.0",
     "django-model-utils==5.0.0",
-    "django-timezone-field==7.0",
+    "django-timezone-field==7.1",
     "certifi==2024.7.4",
     "chardet==5.2.0",
     "idna==3.7",