Function get_object_bytes 

pub async fn get_object_bytes(
    client: &Client,
    bucket: &str,
    key: &str,
    max_bytes: u64,
) -> Result<BytesPayload, AppError>

Fetch the first max_bytes bytes of bucket/key as base64-encoded binary.

Uses a Range: bytes=0-<max_bytes-1> request so large objects are not fully downloaded. Returns a BytesPayload with the base64-encoded body, total content length, ETag, and a truncated flag.

Errors

• AppError::AccessDenied — s3:GetObject permission denied.
• AppError::NotFound — bucket or key does not exist.
• AppError::Network — any other SDK or transport error.