Apply minor UI/UX changes

[Dianaaiym]

• Apply Leah background to "Import Wallet" button on empty state
  https://www.figma.com/design/TnxqoNRnFN5JK1S1xt5CwT/v.-3.0--Unstoppable-Design-System?node-id=3329-13177&t=0RzuT9r0q0HHUaOi-0