fix: category selection, checkout redirect, sidebar shipping visibility

1. Category Selection Bug:
   - Added 'id' alias to category/tag API responses
   - Frontend uses cat.id which was undefined (API returned term_id)

2. Checkout Redirect:
   - Changed from window.location.href + reload to navigate()
   - Added !isProcessing check to empty cart condition

3. Sidebar Shipping for Virtual-Only:
   - Hide Shipping Method section when isVirtualOnly
   - Hide Shipping row in totals when isVirtualOnly

4. License Table:
   - Table creation runs via ensure_tables() on plugins_loaded

includes/Api/ProductsController.php

@@ -621,6 +621,7 @@ class ProductsController {
 		$categories = [];
 		foreach ($terms as $term) {
 			$categories[] = [
+				'id' => $term->term_id,
 				'term_id' => $term->term_id,
 				'name' => $term->name,
 				'slug' => $term->slug,
@@ -649,6 +650,7 @@ class ProductsController {
 		$tags = [];
 		foreach ($terms as $term) {
 			$tags[] = [
+				'id' => $term->term_id,
 				'term_id' => $term->term_id,
 				'name' => $term->name,
 				'slug' => $term->slug,