Give solid.move the copy half of its Move/Copy label (#498)

solid.move takes copy: true to keep the source bodies and transform a new copy of each, with a Create Copy box in the Move dialog. Designs without it save and load exactly as before.

crates/ui-egui/src/locales/de.json

@@ -69,6 +69,7 @@
   "ui.counterbore": "Tiefenbohrung",
   "ui.countersink": "Senkung",
   "ui.create": "Erstellen",
+  "ui.create_copy": "Kopie erstellen",
   "ui.create_sketch": "Skizze erstellen",
   "ui.current": "aktuell",
   "ui.curvature": "Krümmung",