setEnvironment method
Set current environment
Implementation
Future<void> setEnvironment(String envName) async {
if (!environments.containsKey(envName.toLowerCase())) {
throw ArgumentError('Environment "$envName" not found');
}
await _prefs?.setString(_currentEnvKey, envName);
// Mark that user has selected an environment (no longer using default)
await _prefs?.setBool(_hasUserSelectedKey, true);
}