style: remove dashed borders from empty tiles

- Remove border-2 border-dashed border-border-default classes
- Remove hover:border-background-accent class
- Clean, minimal empty tile appearance
- Maintains rounded corners and hover interactions
- Subtle hint dot still visible in center when not hovering

ui/desktop/src/components/peers/PeersView.tsx

@@ -204,8 +204,6 @@ const EmptyPeerTile: React.FC<{ onAddFriend: () => void }> = ({ onAddFriend }) =
         hover:bg-background-medium
         aspect-square
         flex flex-col items-center justify-center
-        border-2 border-dashed border-border-default
-        hover:border-background-accent
         rounded-2xl
       "
     >