A U.S.-backed Kurdish-led force said Monday that a prison overrun by the Islamic State group in northeastern Syria was now fully under its control, thwarting a dangerous plot by the extremists to launch further, multiple attacks across the volatile region. It also appealed for the international community’s help in taking responsibility for the tens of thousands of IS fighters and their families in detention centers and camps under its control. The Syrian Democratic Forces said more than 120 of their fighters and prison workers died in the 10-day standoff at the Gweiran prison, also known as al…