backend: separate App and server, add websocket endpoint, accept data directory command argument. initialize sqlalchemy database and models in new module. frontend: create backend class for managing ws connection, move ui to chat_screen, create scaffold chat and agent classes.

frontend/lib/agent.dart

@@ -0,0 +1,9 @@
+import 'chat.dart';
+
+class Agent {
+  void receivedChatMessage(Chat chat, String message) {
+    // Simple response from the agent
+    String responseMessage = "Agent received: " + message;
+    chat.addAgentMessage(responseMessage);
+  }
+}