feat(cms): CMS-driven homepages, products section, placeholder resolution

- Add ProductCard/ProductsSection schema and _products.html section macro
- Rewrite seed script with 3-platform homepage sections (wizard, OMS, loyalty),
  platform marketing pages, and store defaults with {{store_name}} placeholders
- Add resolve_placeholders() to ContentPageService for store default pages
- Fix SQLAlchemy filter bugs: replace Python `is None` with `.is_(None)` across
  all ContentPageService query methods (was silently breaking all platform page lookups)
- Remove hardcoded orion fallback and delete homepage-orion.html
- Add placeholder hint box with click-to-copy in admin content page editor
- Export ProductCard/ProductsSection from cms schemas __init__

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/cms/templates/cms/admin/content-page-edit.html

@@ -187,6 +187,35 @@
                     </p>
                 </div>
             </div>
+
+            {# Available Placeholders (for store default pages) #}
+            {% set placeholders = [
+                ('store_name', "The store's display name"),
+                ('store_email', "The store's contact email"),
+                ('store_phone', "The store's phone number"),
+            ] %}
+            <div x-show="!form.store_id || form.store_id === 'null'" x-cloak
+                 class="mb-4 p-4 bg-blue-50 dark:bg-blue-900/20 border border-blue-200 dark:border-blue-800 rounded-lg">
+                <h4 class="text-sm font-semibold text-blue-800 dark:text-blue-300 mb-2 flex items-center">
+                    <span x-html="$icon('information-circle', 'w-4 h-4 mr-1.5')"></span>
+                    Available Placeholders
+                </h4>
+                <p class="text-xs text-blue-700 dark:text-blue-400 mb-2">
+                    Use these placeholders in store default pages. They will be automatically replaced with the store's actual information when displayed.
+                </p>
+                <div class="flex flex-wrap gap-2">
+                    {% for name, description in placeholders %}
+                    <code class="px-2 py-1 text-xs bg-blue-100 dark:bg-blue-800/40 text-blue-800 dark:text-blue-300 rounded cursor-pointer hover:bg-blue-200 dark:hover:bg-blue-800/60 transition-colors"
+                          @click="navigator.clipboard.writeText('{% raw %}{{{% endraw %}{{ name }}{% raw %}}}{% endraw %}')"
+                          title="{{ description }} — click to copy">
+                        {% raw %}{{{% endraw %}{{ name }}{% raw %}}}{% endraw %}
+                    </code>
+                    {% endfor %}
+                </div>
+                <p class="text-xs text-blue-600 dark:text-blue-500 mt-2">
+                    Click a placeholder to copy it to your clipboard.
+                </p>
+            </div>
         </div>
 
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