Films trying to capture the fractious, chronically online nature of modern life are inevitably playing catch-up, but they don’t help themselves by adding a hashtag — that musty relic of 2010s social media — to their titles. Arriving in the wake of Daisuke Miyazaki’s “#Mito” and Kazuyoshi Kumakiri’s “#Manhole” (both 2023), King Bai’s “#Viral” is another Faustian tale of internet fame that feels like its moment has already passed.