Bump pillow from 11.1.0 to 12.2.0 in /src/backend

Bumps [pillow](https://github.com/python-pillow/Pillow) from 11.1.0 to 12.2.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@11.1.0...12.2.0)

---
updated-dependencies:
- dependency-name: pillow
  dependency-version: 12.2.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

src/backend/requirements.txt

@@ -10,7 +10,7 @@ django-storages==1.14.6
 django-amazon-ses==4.0.1
 requests==2.32.4
 django-sesame[ua]==3.2.2
-Pillow==11.1.0
+Pillow==12.2.0
 rollbar==0.16.2
 gunicorn==23.0.0
 psycopg2==2.9.10