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

lib/features/auth/presentation/providers/auth_provider.dart

@@ -135,6 +135,7 @@ class AuthNotifier extends StateNotifier<AuthState> {
   Future<void> login({
     required String email,
     required String password,
+    String? loginRole,
   }) async {
     state = state.copyWith(
       status: AuthStatus.loading,
@@ -146,6 +147,7 @@ class AuthNotifier extends StateNotifier<AuthState> {
       final result = await _repository.login(
         email: email,
         password: password,
+        loginRole: loginRole,
       );
 
       if (result['requiresTwoFactor'] == true) {

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,
         );
   }
 

lib/features/auth/presentation/widgets/role_toggle.dart

@@ -23,7 +23,7 @@ class RoleToggle extends StatelessWidget {
         mainAxisSize: MainAxisSize.min,
         children: [
           _buildToggleButton('User', 'USER'),
-          _buildToggleButton('Admin', 'AGENT'),
+          _buildToggleButton('Agent', 'AGENT'),
         ],
       ),
     );