Add custom page template for composable products, bump to v1.3.2

- Custom WooCommerce template with compact header + full-width selector
- Twig layout template (single-product-composable.html.twig) + PHP loader
- Body class 'single-product-composable' for CSS scoping
- Renamed *.twig to *.html.twig (proper naming convention)
- Refreshed .pot with accurate file refs, merged all .po files

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

includes/ProductSelector.php

@@ -73,6 +73,6 @@ class ProductSelector {
 		// Render template — Twig handles escaping via registered esc_html/esc_attr/esc_url functions.
 		$plugin = Plugin::instance();
 		// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- output escaped by Twig template.
-		echo $plugin->render_template( 'product-selector.twig', $context );
+		echo $plugin->render_template( 'product-selector.html.twig', $context );
 	}
 }