Function upload_blob 

pub async fn upload_blob<T>(
    signer: T,
    server_url: &Url,
    file_data: Arc<Vec<u8>>,
    mime_type: Option<&str>,
    read_timeout: Option<Duration>,
) -> Result<String, String>
where
    T: VectorSigner,

Simple upload without progress tracking. read_timeout fast-fails a dead server (see build_http_client_with_options); pass it for small uploads (emoji, avatars) so failover is quick, None for large blobs whose server may go quiet mid-store.