Teenager Anna Chan Wah fought through a sea of demonstrators, undeterred by searing heat, the crawling pace of the protest – and even a gnawing fear of failure.“We know our street protest today is not going to change anything, but we are here to fight for democracy in Hong Kong and to show that we still have a voice,” she said.That was in 2003, when sixth former Chan spoke to the Post during the march against the national security legislation that brought half a million people to the streets…