CAIRO, June 24 (Reuters) - Al-Nazir Al-Sadig sought safety in Egypt from the civil war in Sudan. Instead, the 18-year-old died of pneumonia after more than three weeks in a squalid Cairo jail, where he had suffered beatings and extortion at the hands of other inmates, his friends and relatives said. A high-school student, Al-Sadig was detained as part of what lawyers and human rights groups describe as a sweeping crackdown on refugees that contrasts sharply with Egypt's stated role as a safe haven.