Gunicorn is replaced with nginx-unit

We now serve Netbox with an nginx-unit instance instead of Gunicorn.
This allows us to get rid of the extra Nginx container because Unit is
also serving the static files. The static files are now collected at container
buildtime instead of every startup.

.github/workflows/push.yml

@@ -19,7 +19,7 @@ jobs:
         - ./build.sh develop
         docker_from:
         - '' # use the default of the build script
-        # - python:3.10-rc-alpine # disable until dependencies work
+        - alpine:edge
       fail-fast: false
     runs-on: ubuntu-latest
     name: Builds new Netbox Docker Images