HONG KONG, June 19 (Reuters) - A Hong Kong appeal court on Monday blocked jailed media tycoon Jimmy Lai's bid to challenge in the city's highest court a warrant obtained by national security police to scrutinise the contents of his mobile phones. Lai, 75, is the founder of the now shut pro-democracy newspaper Apple Daily and is due to face trial in September on three charges under the city's sweeping national security law, including collusion with foreign forces. He also faces a charge under the British colonial-era sedition law. Lai is one of the most prominent Hong Kong critics of...