fix(users): refactor user admin actions to return status objects instead of throwing to prevent production error obfuscation

shop/components/admin/user-dialog.tsx

@@ -96,12 +96,17 @@ export function UserDialog({ companies }: UserDialogProps) {
         first_name: values.first_name || undefined,
         last_name: values.last_name || undefined,
       }
-      await createUser(payload)
-      setOpen(false)
-      form.reset()
-      router.refresh()
+      const res = await createUser(payload)
+      if (res.success) {
+        setOpen(false)
+        form.reset()
+        router.refresh()
+      } else {
+        alert(res.error || 'Fehler beim Erstellen des Benutzers.')
+      }
     } catch (error) {
       console.error('Error creating user:', error)
+      alert('Ein unerwarteter Fehler ist aufgetreten.')
     }
   }