refactor: centralise app name validation

cli/app/undeploy.go

@@ -2,7 +2,6 @@ package app
 
 import (
 	"context"
-	"errors"
 
 	"coopcloud.tech/abra/cli/internal"
 	"coopcloud.tech/abra/pkg/client"
@@ -22,10 +21,7 @@ vigilant, as your swarm installation will consider any previously attached
 volumes as eligiblef or pruning once undeployed.
 `,
 	Action: func(c *cli.Context) error {
-		appName := c.Args().First()
-		if appName == "" {
-			internal.ShowSubcommandHelpAndError(c, errors.New("no app name provided"))
-		}
+		appName := internal.ValidateAppNameArg(c)
 
 		appFiles, err := config.LoadAppFiles("")
 		if err != nil {