Being in the White House to witness the president signing legislation aimed at cracking down on sites that facilitate human trafficking and prostitution was a bittersweet moment for Gina A. DeBoni and her client, Yvonne Ambrose.Ambrose’s 16-year-old daughter, Desiree Robinson, was found dead in a Markham garage on Christmas Eve 2016. Robinson was featured in sex solicitation posts on Backpage.com, a classified …