Bug: Audio upload failing with 403 Forbidden due to trailing slash in URL

User is unable to save audio files after a recent update. The error message shows a trailing slash at the end of the .mp3 file path (e.g., .../custom-audio-69e80e2027504.mp3/), resulting in a "403 Forbidden" Access Denied error from AWS S3. User has already tried clearing cache and refreshing. This appears to be a regression in the upload URL formatting.