Bump urllib3 from 2.6.3 to 2.7.0 in /backend

Bumps [urllib3](https://github.com/urllib3/urllib3) from 2.6.3 to 2.7.0.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@2.6.3...2.7.0)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-version: 2.7.0
  dependency-type: indirect
...

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

Author: dependabot[bot]

backend/requirements.txt

@@ -252,7 +252,7 @@ tzdata==2025.2
     # via
     #   kombu
     #   pandas
-urllib3==2.6.3
+urllib3==2.7.0
     # via
     #   django-revproxy
     #   elastic-transport