fix: Properly extract variation attribute values from WooCommerce meta

Fixed empty attribute values in variations.

WooCommerce stores variation attributes in post meta:
- Key format: 'attribute_' + lowercase attribute name
- Example: 'attribute_color' → 'red'

Changes:
1. Try lowercase: attribute_color
2. Fallback to sanitized: attribute_pa-color
3. Capitalize name for display: Color

This should now show:
- Before: {"Color": ""}
- After: {"Color": "Red"} or {"Color": "Blue"}

Test by refreshing edit product page.

includes/Api/ProductsController.php

@@ -608,7 +608,7 @@ class ProductsController {
 					}
 					
 					$attr_name = $parent_attr->get_name();
-					$clean_name = $parent_attr->get_name(); // Already clean for custom attributes
+					$clean_name = $attr_name;
 					
 					// Get the variation's value for this attribute
 					if (strpos($attr_name, 'pa_') === 0) {
@@ -622,8 +622,19 @@ class ProductsController {
 							$value = $term ? $term->name : $value;
 						}
 					} else {
-						// Custom attribute - get from meta
-						$value = get_post_meta($variation_id, 'attribute_' . sanitize_title($attr_name), true);
+						// Custom attribute - get the value from variation meta
+						// WooCommerce stores it as 'attribute_' + lowercase attribute name
+						$meta_key = 'attribute_' . strtolower($attr_name);
+						$value = get_post_meta($variation_id, $meta_key, true);
+						
+						// If not found, try with sanitized title
+						if (empty($value)) {
+							$meta_key = 'attribute_' . sanitize_title($attr_name);
+							$value = get_post_meta($variation_id, $meta_key, true);
+						}
+						
+						// Capitalize the attribute name for display
+						$clean_name = ucfirst($attr_name);
 					}
 					
 					$formatted_attributes[$clean_name] = $value;