Wallos: Cross-user Fixer/API Layer credential consumption in exchange-rate refresh

Wallos is an open-source, self-hostable personal subscription tracker. Prior to version 4.9.1, endpoints/currency/update_exchange.php loads the first Fixer/API Layer credential globally instead of loading the credential for the authenticated user. As a result, a normal authenticated user without their own provider key can trigger exchange-rate refreshes using another user's stored provider credential. This issue has been patched in version 4.9.1.