Missing cancellation mechanism for pending transfers leads to operational inflexibility

The two-step transfer pattern for authority and withdrawal_signer lacks a cancellation mechanism. Once a nomination is initiated, the current authority cannot revoke it, they can only overwrite it with a different nomination. This creates operational inflexibility if a nomination was made in error.

Add cancellation instructions:

pub fn cancel_pending_authority(ctx: Context<CancelPending>) -> Result<()> {
    let transfers = &mut ctx.accounts.pending_transfers;
    transfers.pending_authority = Pubkey::default();
    msg!("Pending authority transfer cancelled");
    Ok(())
}

Fair Casino: Fixed.

Zealynx: Verified.