Refactor code structure for improved readability and maintainability

components/ui/Layout.js

@@ -11,13 +11,15 @@ import {
   XMarkIcon as XIcon,
   UserIcon,
   ArrowRightOnRectangleIcon as LogoutIcon,
-  TruckIcon
+  TruckIcon,
+  CpuChipIcon
 } from '@heroicons/react/24/outline';
 
 const navigationItems = [
   { name: 'Przekrój terenu', href: '/', icon: HomeIcon },
   { name: 'Siatka', href: '/cross', icon: GridIcon },
   { name: 'Uziomy', href: '/uziomy', icon: LightningBoltIcon },
+  { name: 'Spadki napięcia', href: '/spadki', icon: CpuChipIcon },
   { name: 'Śledzenie przesyłek', href: '/tracking', icon: TruckIcon },
 ];