PHILADELPHIA — A federal jury on Thursday found John Dougherty guilty on embezzlement charges, delivering his second felony conviction in as many years and casting a devastating blow to his legacy as one of the region’s most transformative labor leaders. The panel of seven women and five men took roughly 14 hours over three days to conclude that even as Dougherty publicly held himself out as a tireless advocate for his union, Local 98 of the International Brotherhood of Electrical Workers, he was secretly stealing from its members to enrich himself and his family. In all, jurors determined, Do…