DUBAI, United Arab Emirates — The United Nations secretary-general warned Tuesday that the war in Sudan is “spiraling out of control” after a paramilitary force seized the besieged and famine-stricken Darfur city of el-Fasher. Speaking in Qatar, Antonio Guterres called for an immediate ceasefire in the two-year conflict that’s become one of the world’s worst humanitarian crises . “Hundreds of thousands of civilians are trapped by this siege,” Guterres said. “People are dying of malnutrition,