Split template and software repo

GH workflows can access other workflows across repos; see also: https://docs.github.com/en/actions/how-tos/reuse-automations/reuse-workflows#calling-a-reusable-workflow

This would enable shipping updates to workflows ever after a template has been used.
Especially the deploy and backup workflows could be managed by the software repo.

This would also enable us to create more specific templates for common frameworks like Django or Next.js.