feat: add role-based authentication support and update UI toggle label to Agent

lib/features/auth/presentation/screens/login_screen.dart

@@ -53,6 +53,7 @@ class _LoginScreenState extends ConsumerState<LoginScreen> {
     ref.read(authProvider.notifier).login(
           email: _emailController.text.trim(),
           password: _passwordController.text,
+          loginRole: _selectedRole,
         );
   }