Add 500.html and 404.html to the app

[ghost]

The nginx.conf of the product uses a 500.html file, which is not in the application right now

[ghost]

we also have to add it in the existing apps

[ghost]

Please do the following for all products:

• add 404.html and 500.html of this pr to templates/web/deploy/web (or use the 404.html of the app)
• change Dockerfile --> add 'COPY ./deploy/web/*.html /usr/share/nginx/html/'
• change nginx-default.conf as in the pr

Please do the following for all apps:

• remove src/404.html and remove the import in intialize.XX.ts