Setup production-ready backend web-server

[kostmetallist]

Currently, the backend app is launched via built-in Werkzeug development server, which is not appropriate for production environment. More stable and secure server should be incorporated for the production.

Potentially, it can be solved by:

• setting up a reliable WSGI server
• providing means for DEV and PROD configuration separation

[kostmetallist]

See also https://flask.palletsprojects.com/en/2.3.x/deploying/