Update CLI greeting and copyright notice

- Usage: "Kubernetes and OpenShift Backup Operator" (was default
  "A new cli application")
- Copyright: "(c) K8up Authors" (was "(c) 2021 VSHN AG",
  updated to reflect CNCF project ownership)

Fixes #848

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Aarno Aukia <aarno.aukia@vshn.ch>

Author: arska

cmd/k8up/main.go

@@ -63,9 +63,10 @@ func app() *cli.App {
 
 	return &cli.App{
 		Name:      "k8up",
+		Usage:     "Kubernetes and OpenShift Backup Operator",
 		Version:   version,
 		Compiled:  compiled,
-		Copyright: "(c) 2021 VSHN AG",
+		Copyright: "(c) K8up Authors",
 
 		EnableBashCompletion:      true,
 		DisableSliceFlagSeparator: true,