`ForgejoProject.get_files()` not working as expected

[mynk8]

Due to the issue described in ogr#907, the worker crashes when using Fedora 42 with the system-packaged version.

As a temporary workaround, we're using fedora-rawhide. However, celery system package is broken there and needs a rebuild for Python 3.14, so we're relying on the PyPI version (pip install celery).