Preserve explicit model and provider architecture (#30)

frontend/packages/sxchnge_auth/lib/src/services/dummy.dart

@@ -1,3 +1,5 @@
+import '../dto/results.dart';
+import '../mappers/results.dart';
 import '../models/auth.dart';
 import 'contracts.dart';
 import 'verification.dart';
@@ -18,7 +20,9 @@ class DummyLoginService implements LoginService, SimulationInfo {
   Future<AuthResult> login(LoginRequest request) async {
     await Future<void>.delayed(delay);
     if (failure case final error?) throw AuthException(error);
-    return const AuthResult(userId: 'demo-user', isSimulated: true);
+    return AuthMapper.fromDTO(
+      const AuthDTO(userId: 'demo-user', simulated: true),
+    );
   }
 }
 
@@ -36,6 +40,8 @@ class DummySignupService implements SignupService, SimulationInfo {
   Future<AuthResult> signup(SignupRequest request) async {
     await Future<void>.delayed(delay);
     if (failure case final error?) throw AuthException(error);
-    return const AuthResult(userId: 'demo-user', isSimulated: true);
+    return AuthMapper.fromDTO(
+      const AuthDTO(userId: 'demo-user', simulated: true),
+    );
   }
 }