Issue #3538116: Redirect admin shows wrong language prefix in URL display

1. When creating the URL for the redirect, the language context is explicitly set using with the selected redirect language. This ensures that the displayed and clicked redirect links use the appropriate language context.
2. If the redirect entity has an undefined language, or if the selected language is "All languages", the code now defaults to the site's default language to prevent generating invalid URLs.

Closes #3538116