New RPC endpoints: - backup.upload-s3: Upload encrypted backup to any S3-compatible endpoint - backup.download-s3: Download backup from S3 to local storage Supports MinIO, Backblaze B2, Wasabi via basic auth + S3 API. Backups are AES-256-GCM encrypted before upload. Rate-limited at 3 requests per 10 minutes. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>