fix(members): add novalidate to retroactive wizard form to suppress browser validation errors

Native HTML5 constraint validation fires on hidden fields (display:none panels),
causing "not focusable" errors on inst_months. Custom validateStep() handles all
validation — novalidate disables the duplicate browser check.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Modules/Members/Views/retroactive-wizard.php

@@ -48,7 +48,7 @@ if ($wizardAlerts): ?>
         </div>
     </div>
 
-    <form id="retroForm" action="/members/retroactive-wizard" method="POST">
+    <form id="retroForm" action="/members/retroactive-wizard" method="POST" novalidate>
         <?= csrf_field() ?>
 
         <!-- ═══════════════ STEP 1: Basic Info ═══════════════ -->