Build a Users Database UI in React that allows filtering, creating, updating, and deleting users.

Requirements:

1. Display a list of users fetched from an API (https://dummyjson.com/users).
2. Include a search/filter input to filter users by username or email.
3. Allow creating a new user with a form (username, email).
4. Allow editing an existing user’s username or email.
5. Allow deleting a user from the list.
6. Update the UI immediately after create/update/delete actions.
7. Focus on functionality over styling.