feat: display friendly error messages for LDAP authentication failures

[JohnVillalovos]

Wrap authentication validation in try/catch to handle LDAP-related exceptions (missing pear/net_ldap2 library, unreachable LDAP server) and display (hopefully) user-friendly error messages on the login page instead of a generic error or unhandled exception.

This doesn't change the message seen if the issue is a wrong username/password.

[Copilot]

Pull request overview

This PR improves the login experience by catching LDAP-related authentication exceptions and showing a more specific, user-facing error message on the login page instead of an unhandled exception/generic failure.

Changes:

• Wrap LoginPresenter::Login() credential validation in try/catch and map known LDAP failure messages to localized UI strings.
• Add support in LoginPage + template to display an optional login error message override.
• Extend fakes/tests to cover exception-driven authentication failures and the new messaging behavior.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
Presenters/LoginPresenter.php	Catches auth exceptions, logs them, and selects an LDAP-specific message when applicable.
Pages/LoginPage.php	Adds SetLoginErrorMessage() and initializes a LoginErrorMessage template variable.
tpl/login.tpl	Displays LoginErrorMessage when present, otherwise falls back to the existing LoginError translation.
tests/fakes/FakeWebAuthentication.php	Allows the fake Validate() to throw exceptions for presenter tests.
tests/Presenters/LoginPresenterTest.php	Adds test cases for LDAP dependency missing / connection errors / generic exception fallback; updates fake page with new setter.
lang/en_us.php	Adds new localized strings for LDAP dependency missing and connection errors.
lang/de_de.php	Adds the same LDAP error strings in German.
lang/es.php	Adds the same LDAP error strings in Spanish.
lang/ja_jp.php	Adds the same LDAP error strings in Japanese.

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