BECKHAM BY DESIGN: Now that her “Fashion Icons” book is done-and-dusted, Fern Mallis is gearing up for her June 3 Q&A with Victoria Beckham at 92Y. Having shed her “Spice Girls” self years ago, Beckham will delve into her nearly seven-year run as a designer. With 8.3 million Twitter followers, the two-time British fashion award winner and United Nations AIDS ambassador As of last week, there was no word yet as to whether Beckham will have her husband David or any of her four children in tow.