Move the original PHP site into legacy/

The PHP sources, templates and old jQuery-based scripts move unchanged into
legacy/ for reference. Shared assets (media/, images/, favicon.ico, the
default avatar) stay at the repository root.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

legacy/templates/registered.tpl.php

@@ -0,0 +1,7 @@
+<?php include( $templates.'header.tpl.php' ); ?>
+<div class="article">
+<h2>Account successfully created</h2>
+<p>You can now login.</p>
+
+</div>
+<?php include( $templates.'footer.tpl.php' ); ?>