Build a Transfer List component in React that allows moving items between two lists.

Requirements:

1. Display two lists side by side: "Available" and "Selected".
2. Each list should display its items.
3. User should be able to:
   • Move an item from "Available" to "Selected".
   • Move an item from "Selected" back to "Available".
4. Items should not be duplicated; each item should only exist in one list at a time.
5. Focus on functionality over styling.
6. The component should work out-of-the-box in a live React preview (e.g., CodeSandbox/Sandpack).