fix: Update Next.js to 15.5.11 to fix CVE-2025-66478 vulnerability and enhance drag-and-drop UI

- Updated Next.js from 15.1.2 to 15.5.11 (latest secure version)
- Enhanced SpeedGroup drop zone with better visual feedback during drag
- Added pulsing border animation when dragging over drop zones
- Improved empty state with animated icon and contextual messaging
- Enhanced DeviceCard drag state with scale, rotation, and shadow effects
- Added grab/grabbing cursor states for better UX
- Improved visual hierarchy with better spacing and transitions

Author: umerfarok