chore(deps): update pillow requirement in /backend

Updates the requirements on [pillow](https://github.com/python-pillow/Pillow) to permit the latest version.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@10.4.0...11.0.0)

---
updated-dependencies:
- dependency-name: pillow
  dependency-type: direct:production
...

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Author: dependabot[bot]

backend/requirements.txt

@@ -7,5 +7,5 @@ djangorestframework-simplejwt~=5.3.1
 djangorestframework~=3.15.2
 factory-boy~=3.3.0
 gunicorn~=23.0.0
-pillow~=10.4.0
+pillow~=11.0.0
 psycopg2~=2.9.9