User Organization Images Partial Update

Update image asset metadata or replace an image. Request format (JSON): - old_url: URL of the image to update (required) - new_filename: New filename for the image (optional) - image_data: Base64 encoded new image data (optional, for replacement) - content_type: MIME type for new image (optional) Returns: - 200: Image updated successfully - 400: Invalid request - 404: Image not found - 500: Update failed