Remove Snipcart product validation URL to simplify configuration

- Remove data-item-url attribute from product add-to-cart button
- Use direct HTML attributes for Snipcart instead of server-side validation
- Aligns with lapasseggiata project configuration that works without validation endpoint

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

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

site/templates/product.php

@@ -45,7 +45,6 @@
                         data-item-description="<?= $page->description()->excerpt(100) ?>"
                         data-item-image="<?= $page->images()->first() ? $page->images()->first()->url() : '' ?>"
                         data-item-name="<?= $page->title()->html() ?>"
-                        data-item-url="<?= $page->url() ?>/validate.json"
                         <?php
                         if($page->hasOptions()->toBool() && $page->optionValues()->isNotEmpty()):
                             $values = $page->optionValues()->split(',');