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/backend.dart

@@ -0,0 +1,49 @@
+import 'dart:html';
+import 'dart:convert';
+
+class Backend {
+  static WebSocket? _socket;
+  static String? _url;
+
+  static void setup(String url) {
+    _url = url;
+    connect();
+  }
+
+  static void auth(username) {
+    _socket!.send(
+        json.encode({'username': username})
+    );
+  }
+
+  static void connect() {
+    _socket = WebSocket(_url!);
+    _socket!.onOpen.listen((event) {
+      print('Connected to the WebSocket server');
+      auth("the-user");
+      ping(); 
+    });
+    _socket!.onError.listen((event) {
+      print('Error: $event');
+      _reconnect();
+    });
+    _socket!.onClose.listen((event) {
+      print('Disconnected. Attempting to reconnect...');
+      _reconnect();
+    });
+  }
+
+  static void _reconnect() {
+    Future.delayed(Duration(seconds: 5), () {
+      connect();
+    });
+  }
+
+  static void ping() {
+    if (_socket != null && _socket!.readyState == WebSocket.OPEN) {
+      final data = json.encode({'path': 'ping'});
+      _socket!.send(data);
+      print('Ping sent: $data');
+    }
+  }
+}