ST. ANTHONY’S MONASTERY, Egypt — In a cave high in the desert mountains of eastern Egypt, the man said to be the father of monasticism took refuge from the temptations of the world some 17 centuries ago. At the foot of the mountain, the monks at the St. Anthony’s Monastery bearing his name continue the ascetic tradition. But even this remote spot is touched by the turbulent times facing Egypt’s Christians, who fear for their future under the rising power of Islamists.