Well, in your case, it would be good to add the line with the {site_url} word to the template like Studio->Polyglot->Notifications->New notification so it will look like:

{email_header}
<p> </p>
{content}
<p> </p>
{site_url}
{email_footer}

In other case, it will require the editing the code of every app to transform the links in text like {content}