TICKET: SC-5648

Summary:

• Change fromAddressesBytes from [userAddress] to sorted _fromAddresses

• Sort fromAddressesBytes before passing to FlareJS to match sorted UTXO addresses

• Fixes 'No addresses match UTXO owners' error in HSM firmware tests

• Clarify comments about reward distribution (determined by stake output addresses, not rewardAddresses parameter)"

• Change output threshold

  • Issue: FlareJS defaults change outputs to threshold=1 for multisig wallets
  • Impact: Any single compromised key could steal change funds
  • Fix: Apply threshold correction (same pattern as ExportInPTxBuilder)

• Add comprehensive test coverage (33 tests)

  • Core validation (nodeID, amount, duration, required fields)
  • BitGo multisig patterns (2-of-3, 2-of-2)
  • Multiple UTXOs, change outputs, round-trip serialization
  • Real-world scenarios (multiple/sequential delegations)