Bump django from 5.2.8 to 6.0.4 in /backend

Bumps [django](https://github.com/django/django) from 5.2.8 to 6.0.4.
- [Commits](django/django@5.2.8...6.0.4)

---
updated-dependencies:
- dependency-name: django
  dependency-version: 6.0.4
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

backend/pyproject.toml

@@ -44,7 +44,7 @@ known-first-party = [
 [project]
 requires-python = ">=3.13.5"
 dependencies = [
-    "django==5.2.8",
+    "django==6.0.4",
     "django-environ==0.10.0",
     "django-model-utils==5.0.0",
     "django-timezone-field==7.0",