By Leon Malherbe and Parisa Hafezi BERLIN/DUBAI (Reuters) -Tens of thousands of people marched in Berlin on Saturday in a show of support for protesters in Iran where unrest ignited by Mahsa Amini’s death in police custody entered a sixth week despite a deadly state crackdown. The protests have posed one of the boldest challenges to Iran’s clerical leadership since the 1979 revolution, even if they do not appear close to toppling a government that has deployed its powerful security apparatus to quell the unrest. Amini, a 22-year-old Iranian Kurd, died in the custody of morality police after be…