PIRAEUS, Greece, March 5 (Reuters) - Greek seafarers began a 24-hour strike on Thursday, halting local ferry services, as they protested over vessel crews stranded in the Gulf amid the escalating Middle East war, and demanded the area is declared a war risk zone to enable their repatriation. The Iran conflict threatens Gulf ports and has already disrupted global trade through the Strait of Hormuz, a key artery accounting ​for about 20% of global oil and gas supply. Although the Strait is not sh...