fix(lib): show error message detail when hitting some common flows

Instead of giving the user nothing to go off of, this patch gives them
an opaque blob of ROT-13 encoded base64. The logic is that if you are
smart enough to figure out how to decode this, you're probably smart
enough to either fix your broken client or give it to the adminstrator.

Signed-off-by: Xe Iaso <me@xeiaso.net>

web/index.templ

@@ -88,10 +88,13 @@ templ base(title string, body templ.Component, impressum *config.Impressum, chal
 	</html>
 }
 
-templ errorPage(message, mail string, localizer *localization.SimpleLocalizer) {
+templ errorPage(message, mail, code string, localizer *localization.SimpleLocalizer) {
 	<div class="centered-div">
 		<img id="image" alt="Sad Anubis" style="width:100%;max-width:256px;" src={ anubis.BasePrefix + "/.within.website/x/cmd/anubis/static/img/reject.webp?cacheBuster=" + anubis.Version }/>
 		<p>{ message }.</p>
+		if code != "" {
+			<code><pre>{ code }</pre></code>
+		}
 		if mail != "" {
 			<p>
 				<a href="/">{ localizer.T("go_home") }</a> { localizer.T("contact_webmaster") }