Bread can — and does — sustain us, even under the most economically stretched conditions — It’s 2:15 a.m. and I am humming the tune of “Ederlezi,” approaching the Suada and Olga Bridge toward the Grbavica district of Sarajevo, Bosnia, where I have rented a room. Grbavica had suffered heavy shelling in the 1990s when Sarajevo was under siege by nationalist Serbs. Window sills bloom with…