[Cropperjs] Drop explicit white rotate background

v4's Config::$backgroundColor already defaults to 'ffffff', and
rotate(angle, null) falls back to it, so passing 'ffffff' explicitly is
redundant. Omitting it keeps the same white-corner output while letting
a custom driver_service ImageManager control the fill via its own config.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: deluxetom

src/Cropperjs/src/Model/Crop.php

@@ -61,7 +61,7 @@ public function getCroppedThumbnail(int $maxWidth, int $maxHeight, string $forma
         $image->scaleDown($maxWidth, $maxHeight);
 
         if (!empty($this->options['rotate'])) {
-            $image->rotate($this->options['rotate'], 'ffffff');
+            $image->rotate($this->options['rotate']);
         }
 
         return (string) $image->encodeUsingFileExtension($format, quality: $quality);
@@ -77,7 +77,7 @@ public function getCroppedImage(string $format = 'jpg', int $quality = 80): stri
         }
 
         if (!empty($this->options['rotate'])) {
-            $image->rotate($this->options['rotate'], 'ffffff');
+            $image->rotate($this->options['rotate']);
         }
 
         return (string) $image->encodeUsingFileExtension($format, quality: $quality);