More than four months after Katrina wrecked much of the city, law firms such as Bruno & Bruno have filed dozens of lawsuits that reflect the rising frustration and anger among thousands of residents and business owners who lost homes, jobs and relatives in the flooding. The lawsuits’ targets include the U.S. Army Corps of Engineers and local government boards that oversaw New Orleans’ failed levees, as well as an oil company, a nursing home and insurers. The growing pile of litigation is hitting a court system that is still struggling to recover from the disruptions caused by the flooding and evacuations that followed the Aug. 29 storm.