THE wail of police sirens is back and gunfire again punctuates the night. As drug dealers move into flood-damaged houses, alarmed residents say that in the past few weeks they have begun to sense a return to the bad old days before Hurricane Katrina, when crime was an omnipresent straitjacket on life in New Orleans. In a city that once led the nation in homicides per capita, crime has long been a leading indicator of New Orleans's health and prospects - an unavoidable part of the equation for a walk around the block or a trip to the grocery store....