How a store installs this
One script site-wide + a button that names the product by SKU. Everything else comes from the synced catalog.
// once, site-wide (e.g. theme.liquid)
<link rel="stylesheet" href="https://yourhost/widget.css">
<script src="https://yourhost/widget.js" data-fv-api="https://yourhost" data-fv-key="pk_live_xxx" defer></script>
// on each product page
<button data-fv-button data-fv-sku="{{ product.selected_or_first_available_variant.sku }}">See it in your room</button>