fix(abstract-utxo): correct fee calculation in backup recovery

Fix dimension calculation for backup key recovery to include the recovery
destination output. Without this, the approximated transaction fee would
be incorrect, potentially creating transactions with insufficient fees.

Issue: BTC-2891

Co-authored-by: llm-git <[email protected]>

Author: OttoAllmendinger

modules/abstract-utxo/src/recovery/backupKeyRecovery.ts

@@ -341,10 +341,6 @@ export async function backupKeyRecovery(
       ? params.feeRate
       : await getRecoveryFeePerBytes(coin, { defaultValue: DEFAULT_RECOVERY_FEERATE_SAT_VBYTE_V2 });
 
-  // KRS recovery transactions have a 2nd output to pay the recovery fee, like paygo fees.
-  const dimensions = Dimensions.fromPsbt(psbt).plus(isKrsRecovery ? Dimensions.SingleOutput.p2wsh : Dimensions.ZERO);
-  const approximateFee = BigInt(dimensions.getVSize() * feePerByte);
-
   txInfo.inputs =
     responseTxFormat === 'legacy'
       ? unspents.map((u) => ({ ...u, value: Number(u.value), valueString: u.value.toString(), prevTx: undefined }))
@@ -354,6 +350,13 @@ export async function backupKeyRecovery(
     utxolib.bitgo.addWalletUnspentToPsbt(psbt, unspent, walletKeys, 'user', 'backup');
   });
 
+  const dimensions = Dimensions.fromPsbt(psbt)
+    // Add the recovery output
+    .plus(Dimensions.fromOutput({ script: utxolib.address.toOutputScript(params.recoveryDestination, coin.network) }))
+    // KRS recovery transactions have a 2nd output to pay the recovery fee, like paygo fees.
+    .plus(isKrsRecovery ? Dimensions.SingleOutput.p2wsh : Dimensions.ZERO);
+  const approximateFee = BigInt(dimensions.getVSize() * feePerByte);
+
   let krsFee = BigInt(0);
   if (isKrsRecovery && params.krsProvider) {
     try {