fix: do not require a local image for k3s deploys

Kubernetes pulls the app image itself, so a k3s host is free to reap its local copy while the workload keeps running, which the `registry` plugin already does on its own. Deploys, restarts, `dokku run`, and in-cluster cron no longer assert that the image is present locally, falling back to the metadata recorded in the app's current Helm release. A `ps:restart` naming a single process type now rolls only that process type's pods rather than silently redeploying every one. Apps with an `app.json` postdeploy task still require the image locally, as that task runs on the Dokku host.

plugins/scheduler-k3s/preview.go

@@ -69,6 +69,7 @@ func CommandPreview(appName string, diffContext int, showSecrets bool, showSecre
 	buildOpts := BuildOptions{AllowMissingImage: true}
 	if currentRelease != nil {
 		buildOpts.OverrideDeploymentID = deploymentIDFromRelease(currentRelease)
+		buildOpts.FallbackImageMetadata = imageMetadataFromValues(releaseValues(helmAgent, appName))
 	}
 
 	chartResult, err := BuildAppChart(ctx, appName, "", buildOpts)