feat: category filter, item reference SKU lookup, brand sync, and on-demand BC write-back

- Filter product sync to an allow-list of BC item category codes
- Look up items by ReferenciasArticulo item reference before falling back to GTIN/item number
- Sync BC item category to product_brand and parent category to product_cat via a new ItemCategoryHierarchy endpoint
- Add on-demand push of product name/photo back to BC (product edit meta box + bulk action), including binary PATCH support for item pictures

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

woo-business-central/includes/class-wbc-api-client.php

@@ -498,4 +498,67 @@ class WBC_API_Client {
 
         return self::get( '/items', $params );
     }
+
+    /**
+     * PATCH raw binary content to an endpoint (e.g. item picture upload)
+     *
+     * @param string $endpoint     API endpoint (e.g. '/items(id)/picture/pictureContent').
+     * @param string $binary_data  Raw binary body.
+     * @param string $content_type MIME type of the binary content.
+     * @return true|WP_Error True on success (204), or error.
+     */
+    public static function patch_binary( $endpoint, $binary_data, $content_type ) {
+        $token = WBC_OAuth::get_access_token();
+
+        if ( is_wp_error( $token ) ) {
+            return $token;
+        }
+
+        $url = self::build_url( $endpoint, true );
+
+        WBC_Logger::debug( 'API', 'PATCH binary request', array( 'url' => $url, 'content_type' => $content_type ) );
+
+        $ch = curl_init();
+
+        curl_setopt_array( $ch, array(
+            CURLOPT_URL            => $url,
+            CURLOPT_RETURNTRANSFER => true,
+            CURLOPT_TIMEOUT        => self::TIMEOUT,
+            CURLOPT_CUSTOMREQUEST  => 'PATCH',
+            CURLOPT_POSTFIELDS     => $binary_data,
+            CURLOPT_HTTPHEADER     => array(
+                'Authorization: Bearer ' . $token,
+                'Content-Type: ' . $content_type,
+                'If-Match: *',
+            ),
+        ) );
+
+        $response = curl_exec( $ch );
+        $http_code = curl_getinfo( $ch, CURLINFO_HTTP_CODE );
+        $curl_error = curl_error( $ch );
+
+        curl_close( $ch );
+
+        if ( $response === false ) {
+            WBC_Logger::error( 'API', 'cURL error on binary PATCH', array( 'error' => $curl_error, 'url' => $url ) );
+            return new WP_Error( 'wbc_curl_error', $curl_error );
+        }
+
+        if ( $http_code >= 400 ) {
+            $data = json_decode( $response, true );
+            $error_message = isset( $data['error']['message'] ) ? $data['error']['message'] : __( 'API request failed', 'woo-business-central' );
+
+            WBC_Logger::error( 'API', 'Binary PATCH failed', array(
+                'http_code' => $http_code,
+                'error'     => $data['error'] ?? null,
+                'url'       => $url,
+            ) );
+
+            return new WP_Error( 'wbc_api_error', $error_message, array( 'status' => $http_code ) );
+        }
+
+        WBC_Logger::debug( 'API', 'Binary PATCH successful', array( 'http_code' => $http_code, 'url' => $url ) );
+
+        return true;
+    }
 }