By Wojciech Kosc in Warsaw Every morning, as millions of caffeine-deprived, peckish Poles set out to tackle their daily errands, they find a brief sanctuary beneath the gleaming green sign of Zabka—Polish for “little frog.” As they pick up their coffees and sandwiches, along with an eclectic mix of items ranging from their favourite weekly magazine to pet food, and perhaps a shot of vodka or a deep-frozen pizza, their choices will influence the performance of the latest company to go public on the Warsaw Stock Exchange. The Polish convenience store chain Zabka is set to make a significant mark…