Own preview and recording workers

src/app.h

@@ -85,7 +85,7 @@ public:
     std::string work_path{ "." };
     std::string rec_path{ "." };
     std::string tmp_path{ "." };
-    std::thread rec_thread;
+    std::jthread rec_thread;
     bool rec_running = false;
     int rec_count = 0;
     std::mutex rec_mutex;