Keeps the credential decryption secret out of the URL, so it no longer lands in web-server access logs, proxy logs, or browser history. credentials/read.php now reads api_key_decrypt_password from the request body, matching create/update. Consumers reading decrypted credentials must send it in the body, not the query string.
API keys now run as a user and inherit that user's module, operation, and client permissions. Drops per-key client scoping and removes existing keys (must be recreated). Adds an edit modal to change a key's user.
