SEOUL – For BTS ARMY members, as the K-pop phenomenon’s fan base is known, the timing of Jin’s discharge from South Korean military service couldn’t have been more fortuitous.Just 24 hours after the oldest member of the world’s biggest boyband was discharged from duty, the South Korean capital was overtaken by BTS fans, with tens of thousands of people lining up Thursday to join the group’s annual party.Organised by HYBE, the band’s agency, the BTS FESTA last year saw 400,000 fans attend.This year’s event, held at a sprawling sports complex in southern Seoul, is expected to exceed the…