LOS ANGELES — The day after her house burned down, Lara Ganz sent a group message to the youth theater troupe she runs: They would not let the Los Angeles firestorm stop their upcoming show. “So many of our castmates have lost everything,” wrote Ganz, the director of youth theater at a beloved playhouse in the Pacific Palisades. “We will continue with rehearsals. I am confident we will find a stage.” The devastating Jan. 7 fire gutted every inch of the 125-seat Pierson Playhouse, from the basement to the roof, leaving behind only a mangled steel skeleton. Many of the