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/osal/startupmanager/startupmanager.v

@@ -222,7 +222,7 @@ pub fn (mut sm StartupManager) delete(name string) ! {
 			}
 		}
 		else {
-			panic('to implement, startup manager only support screen & systemd for now  ${mycat}')
+			panic('to implement, startup manager only support screen & systemd for now  ${sm.cat}')
 		}
 	}
 }
@@ -280,7 +280,7 @@ pub fn (mut sm StartupManager) status(name string) !ProcessStatus {
 			}
 		}
 		else {
-			panic('to implement, startup manager only support screen & systemd for now  ${mycat}')
+			panic('to implement, startup manager only support screen & systemd for now  ${sm.cat}')
 		}
 	}
 }
@@ -303,7 +303,7 @@ pub fn (mut sm StartupManager) output(name string) !string {
 			return systemd.journalctl(service: name)!
 		}
 		else {
-			panic('to implement, startup manager only support screen & systemd for now  ${mycat}')
+			panic('to implement, startup manager only support screen & systemd for now  ${sm.cat}')
 		}
 	}
 }
@@ -326,7 +326,7 @@ pub fn (mut sm StartupManager) exists(name string) !bool {
 			return zinitfactory.exists(name)
 		}
 		else {
-			panic('to implement. startup manager only support screen & systemd for now  ${mycat}')
+			panic('to implement. startup manager only support screen & systemd for now  ${sm.cat}')
 		}
 	}
 }
@@ -347,7 +347,7 @@ pub fn (mut sm StartupManager) list() ![]string {
 			return zinitfactory.names()
 		}
 		else {
-			panic('to implement. startup manager only support screen & systemd for now:  ${mycat}')
+			panic('to implement. startup manager only support screen & systemd for now:  ${sm.cat}')
 		}
 	}
 }

lib/osal/systemd/systemd_process.v

@@ -37,9 +37,6 @@ pub fn (mut self SystemdProcess) write() ! {
 
 	servicecontent := $tmpl('templates/service.yaml')
 
-	println(self)
-	println(servicecontent)
-
 	p.write(servicecontent)!
 }
 
@@ -54,6 +51,7 @@ pub fn (mut self SystemdProcess) start() ! {
 
 	_ = osal.execute_silent(cmd)!
 	self.refresh()!
+	console.print_header('started systemd process: ${self.name}')
 }
 
 // get status from system