Cook the macaroni in boiling water for 8 to 10 minutes, or according to package instructions. Drain, rinse, and transfer to a large bowl. Slice the hard-boiled eggs in half, remove the yolks, and place them in a small bowl. Chop the egg whites and add them to the pasta bowl. Mash the yolks with a fork, then mix in the Greek yogurt, mayonnaise, and mustard until smooth. Add the diced onion and chopped celery to the pasta bowl, then stir in the egg yolk mixture until everything is well combined. Garnish with fresh chives, paprika, and salt to taste. The salad can be eaten right away, but it’s best if chilled in the refrigerator for at least one hour. When serving leftovers, add extra mayonnaise or yogurt if needed to maintain creaminess.