fix(portal): widen registration wizard sidebar from md-3 to md-4

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/portal/src/pages/register/[eventSlug].vue

@@ -487,7 +487,7 @@ async function onSubmit() {
         <VCol
           v-if="mdAndUp"
           cols="12"
-          md="3"
+          md="4"
         >
           <div class="pa-5 pt-8">
             <div
@@ -598,7 +598,7 @@ async function onSubmit() {
         <!-- Step content -->
         <VCol
           cols="12"
-          :md="mdAndUp ? 9 : 12"
+          :md="mdAndUp ? 8 : 12"
         >
           <VCard
             variant="flat"