Configurable image path

[janno42]

For the "EvaP light" instance described in #2763, we would also like to be able to change the branding.
This moves images to their own directory, which can be replaced in the settings so we can use files from a different directory if needed.

[janno42]

I need assistance with the mypy errors :/

[niklasmohrin]

I think we could make the type error go away by changing the setting to be a tuple instead of a list.

However, it seems more sensible to me to delete the view in development (I think it is left from our old way of doing frontend tests), and use a "get static" helper from Django in the staff view

[janno42]

What do you mean by "helper from Django"?

[niklasmohrin]

I think we should use finders.find from https://docs.djangoproject.com/en/6.1/ref/contrib/staticfiles/#finders-module instead of assuming that that the sample excel file is in exactly the first static directory from the setting

[janno42]

We also use settings.STATICFILES_DIRS[0] in these files:

• evaluation/management/commands/scss.py
• evaluation/management/commands/ts.py
• evaluation/tests/test_commands.py

Should these also be changed?

[niklasmohrin]

I think for the development commands the change is not as important (we don't expect a changed value for STATICFILES_DIRS); we should think about it, but we can do that in another PR