HONG KONG, June 30 (Reuters) - Hong Kong's pro-democracy online Citizens' Radio station will cease operations on Friday owing to what its founder described as a "dangerous" political situation and the freezing of its bank account. Launched in 2005 by veteran activist Tsang Kin-shing, the Cantonese-language broadcaster gained a steady following for its hard-hitting talkshows that were critical of authorities, as well as its years-long campaign for press freedom. Its closure represents a further erosion of Hong Kong's media diversity, critics say, with a China-imposed national security law having already led to the shutting of other liberal outlets including the...