By the time most Park Avenue residents wake up and reach for their coffee, Charles Vega is already there. He has been there, at the same white-glove building on the same stretch of Manhattan’s most storied corridor, for nearly 15 years.  He started at 19. He will turn 34 in December. In that time, he has sorted the mail, wrestled with the garbage, fixed laptops for elderly shareholders, held children while parents ran errands, entertained kids who will want a ride on the luggage cart, and