There I was on a weeknight in Paris’s 18th arrondissement, standing under multicolored tea lights strung from what seemed like the sky. Around me, hundreds of Parisians were jumping up and down to a live band performing “Le Freak.” Handsome men and a few women in uniform wove through the sweaty crowd in a conga line. It may have felt like a New York bar mitzvah circa 1998, but it was the annual Bal des Pompiers: the French firemen’s ball…