The French are betting audiences want their epics back. For much of the 1980s and ’90s, France regularly mounted sprawling prestige productions on a scale few European industries could match. Films like Jean-Paul Rappeneau’s  Cyrano de Bergerac  (1990),   Claude Berri’s  Germinal  (1993), or Patrice Chéreau’s  Queen Margot  (1994). But as production costs rose and financing grew more risk-averse, those ambitious historical spectacles gradually disappeared from the big screen, replaced by smaller auteur dramas, comedies and internationally portable genre films. Now, after years in retreat, large-scale French period storytelling is mounting a comeback.…