Fix licenses endpoint 404 error in customer account

- Register licenses query var with WooCommerce via woocommerce_get_query_vars
- Register endpoint in Installer before flushing rewrite rules
- Existing installations need to re-save permalinks

The endpoint was not being recognized because WooCommerce's My Account
requires both add_rewrite_endpoint() and query var registration.

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

src/Installer.php

@@ -35,7 +35,10 @@ final class Installer
         // Set version in options
         update_option('wc_licensed_product_version', WC_LICENSED_PRODUCT_VERSION);
 
-        // Flush rewrite rules for REST API
+        // Register the licenses endpoint before flushing rewrite rules
+        add_rewrite_endpoint('licenses', EP_ROOT | EP_PAGES);
+
+        // Flush rewrite rules for REST API and My Account endpoints
         flush_rewrite_rules();
     }