Pull Request resolves # .

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

The "Authentication - Cookie" plugin logs a security message when a remember-me login fails because the stored token does not match (possible stolen/guessed cookie). The message uses the language string PLG_AUTHENTICATION_COOKIE_ERROR_LOG_LOGIN_FAILED, but onUserAuthenticate()
never loads the plugin's language file, so the raw language key is written to the log instead of the translated text.

This PR adds $this->loadLanguage(); in onUserAuthenticate(), consistent with onPrivacyCollectAdminCapabilities() in the same plugin, which already loads the language before using Text. The string is now translated before it is passed to Log::add().

Testing Instructions

1. Make sure the "Authentication - Cookie" plugin is enabled and that error logging is on (everything.php / category security).
2. On the frontend, log in with the "Remember Me" box checked. This creates a row in #__user_keys and a joomla_remember_me_* cookie.
3. Simulate a token mismatch: in the browser dev tools edit that cookie and change the part before the dot (the token), leaving the part after the dot (the series) unchanged. (Alternatively, change the token value of the matching row in #__user_keys to a wrong hash.)
4. Reload a frontend page so the cookie authentication runs.
5. Open the log file (administrator/logs/everything.php) and look at the security entry.

Actual result BEFORE applying this Pull Request

The log contains the untranslated language key:

PLG_AUTHENTICATION_COOKIE_ERROR_LOG_LOGIN_FAILED

Expected result AFTER applying this Pull Request

The log contains the translated message, e.g.:
Cookie login failed for user 0.

Yes, for user 0. This is another bug and will be fixed later!

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed