feat(sdk-core): add kycHash to StakeOptions for XDC masternode

Add optional kycHash field to StakeOptions interface to support XDC
masternode staking. The field carries the IPFS CID of the KYC document
uploaded via the staking-service KYC upload endpoint before staking.

stakingWallet.stake() spreads all StakeOptions fields into the POST
body automatically, so no further changes are needed.

Ticket: SC-6159

Author: Doddanna17

modules/sdk-core/src/bitgo/staking/iStakingWallet.ts

@@ -162,6 +162,11 @@ export interface StakeOptions {
    * region for eth staking
    */
   region?: string;
+
+  /**
+   * XDC masternode KYC document hash — IPFS CIDv0 (Qm...) or CIDv1 (bafy...)
+   */
+  kycHash?: string;
 }
 
 export interface TronStakeOptions extends StakeOptions {