refactor: improve installer code

- Refactor installer code for better readability and maintainability.
- Move `dagu_server.vsh` to `examples/virt/daguserver/dagu_server.vsh`.
- Remove unnecessary `println` statements.
- Improve error handling in `zinit_installer_actions.v`.
- Update `zinit_installer_actions.v` startup type to systemd.
- Refactor several factory functions.

lib/installers/lang/python/python_actions.v

@@ -8,7 +8,6 @@ import freeflowuniverse.herolib.core.texttools
 import freeflowuniverse.herolib.installers.ulist
 import os
 
-
 //////////////////// following actions are not specific to instance of the object
 
 // checks if a certain version or above is installed