fix: support --global on cron:set

`cron:set --global` wrote the property but emitted `unknown flag: --global` because the post-set `scheduler-cron-write` trigger received `--global` as the appName arg, which pflag rejected before reaching the trigger body.

The trigger args now omit appName for global writes, and the `scheduler-k3s` cron-write trigger short-circuits when called without an app since per-app reconciliation requires a real app name. The docker-local trigger already regenerates the global crontab from all apps so global `mailfrom`/`mailto` are picked up without any further changes.

plugins/cron/subcommands.go

@@ -192,9 +192,13 @@ func CommandSet(appName string, property string, value string) error {
 
 	common.CommandPropertySet("cron", appName, property, value, validProperties, globalProperties)
 	scheduler := common.GetAppScheduler(appName)
+	triggerArgs := []string{scheduler, appName}
+	if appName == "--global" {
+		triggerArgs = []string{scheduler}
+	}
 	_, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
 		Trigger:     "scheduler-cron-write",
-		Args:        []string{scheduler, appName},
+		Args:        triggerArgs,
 		StreamStdio: true,
 	})
 	return err