TYBEE ISLAND — Built by the Army in 1930, the Tybee Post Theater showed its last movie five decades ago and had fallen into disrepair by the time a developer sought to demolish it in 1999. Historic preservationists managed to save the old brick theater. Now after years of restoration work paid for by more than $1 million in fundraising, Tybee Island's only movie theater is expected to reopen this spring.