This would require www-data to be able to write the secret key now.
That would not be an issue in general, but requires awkward changes
with no real use. Users are supposed to configure a secret key
themselves.

Advances #403

This removes the need to have host and port as environment
variables (we might get it in a YAML file from a K8s ConfigMap, or
some such). Also, it ensures that the system answering is a database
rather than an IoT Waffeleisen with a bad taste in port selection.

After all, it is not an entrypoint anymore

Celery can now be started together with uWSGI if one wants to do that

The database needs to be migrated before compiling SCSS, as the SCSS
references a site preference.