logout method
Logs out the current user.
It attempts to call the logout API, then clears all authentication data
from shared_preferences
and resets the provider's state.
Implementation
Future<void> logout() async {
_setLoading(true);
try {
await _apiService.logout();
} catch (e) {
debugPrint('Logout API call failed: $e');
}
await _clearAuthData();
_setLoading(false);
}