only default UPLOAD_FOLDER works with the chat

[ReimarBauer]

When using a different UPLOAD_FOLDER than the default the chat application does not show an uploaded image

% more mscolab_settings.py
import os

DATA_DIR='/tmp/mss'
UPLOAD_FOLDER=os.path.join(DATA_DIR, 'uploadshaha')

the file is stored on the dir, but it is not shown

% cd  /tmp/mss/uploadshaha/9
% ls
Bildschirmfoto_2026-03-11_um_12.08.17-20260311T123417-7FCUMOsMSWp4kHNVma8BVGfNETRe3Mmwo6xzFIgP8xg.png

chat_upload_viewing_on_different_path_not_working.mp4

We need a test for verification

[ReimarBauer]

on hold until the blueprints refactoring is done