feat: Add optional agentTypeId field to RegisterRequest model.

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

@@ -168,6 +168,7 @@ class AuthNotifier extends StateNotifier<AuthState> {
     required String email,
     required String password,
     required String role,
+    String? agentTypeId,
   }) async {
     state = state.copyWith(
       status: AuthStatus.loading,
@@ -188,6 +189,7 @@ class AuthNotifier extends StateNotifier<AuthState> {
           role: role,
           firstName: firstName,
           lastName: lastName,
+          agentTypeId: role == 'AGENT' ? agentTypeId : null,
         ),
       );