feat: integrate Quill rich text editor in admin templates

- Add Quill editor to content-page-edit.html
- Add Quill editor to vendor-product-edit.html
- Add Quill snow theme CSS
- Update background-tasks.html and platform-homepage.html templates

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

app/templates/admin/background-tasks.html

@@ -14,7 +14,7 @@
 {% block content %}
 {% call page_header_flex(title='Background Tasks', subtitle='Monitor running and completed background tasks') %}
     <!-- Flower Dashboard Link (Celery Monitoring) -->
-    <a href="{{ config.FLOWER_URL | default('http://localhost:5555', true) }}"
+    <a href="{{ flower_url }}"
        target="_blank"
        rel="noopener noreferrer"
        class="flex items-center px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-purple-600 border border-transparent rounded-lg active:bg-purple-600 hover:bg-purple-700 focus:outline-none focus:shadow-outline-purple mr-2"
@@ -253,7 +253,7 @@
                             </td>
                             <td class="px-4 py-3 text-sm">
                                 <template x-if="task.celery_task_id">
-                                    <a :href="'{{ config.FLOWER_URL | default('http://localhost:5555', true) }}/task/' + task.celery_task_id"
+                                    <a :href="'{{ flower_url }}/task/' + task.celery_task_id"
                                        target="_blank"
                                        rel="noopener noreferrer"
                                        class="text-purple-600 hover:text-purple-800 dark:text-purple-400 dark:hover:text-purple-300 underline"