Refine poadman setup for maintainability

Description of the issue

Since recent release v1.9.0 the podman production deployment setup is available.

Now we got some reviews and found some enhancements that whill help to make deployment and maintainemance better. This will also clear up the remaining fog on how to reproduce the install on other system setups.

Additionally we worked on app monitoring and also on infrastructure monitoring. The secodn one we are still quite erarly in but got some good plan already. We will work on that in '######'

Ideas of solution

• Use Podman secrets & modularize env files.
• Provide a fleixibilty setting to adjust the place for the postgres data storage location.
• Fix up docs with these changes and apply some readability enhacements.

Workflow checklist

• I am aware of the workflow in
  CONTRIBUTING.md