fix: resolve JS errors on messages and platform-homepage pages

- messages.js: Add missing `error` property required by error_state macro
- platform-homepage.html: Use `<template x-if>` instead of `x-show` to
  prevent Alpine from evaluating `page.template` when `page` is null

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/templates/admin/platform-homepage.html

@@ -33,7 +33,8 @@
 {{ alert_dynamic(type='success', message_var='successMessage', show_condition='successMessage') }}
 
 <!-- Main Form -->
-<div x-show="!loading && page" class="bg-white dark:bg-gray-800 rounded-lg shadow-md overflow-hidden">
+<template x-if="!loading && page">
+<div class="bg-white dark:bg-gray-800 rounded-lg shadow-md overflow-hidden">
     <form @submit.prevent="savePage()">
         <!-- Template Selection -->
         <div class="p-6 border-b border-gray-200 dark:border-gray-700">
@@ -213,6 +214,7 @@
         </div>
     </form>
 </div>
+</template>
 {% endblock %}
 
 {% block extra_scripts %}

static/admin/js/messages.js

@@ -20,6 +20,7 @@ function adminMessages(initialConversationId = null) {
 
         // Loading states
         loading: true,
+        error: null,
         loadingConversations: false,
         loadingMessages: false,
         sendingMessage: false,