test(canton): golden-test EVM transaction encoding against viem

[Pessina]

Follow-up from PR #740.

Code:

• mpc/chain-signatures/node/src/indexer_canton/mod.rs

  Lines 98 to 101 in 93c8e00

  	/// TODO(test): golden-test against viem's `serializeTransaction` with known
  	/// EvmTransactionParams. Verify the output matches byte-for-byte — this is
  	/// what gets hashed and signed, so any divergence breaks on-chain verification.
  	fn encode_unsigned_eip1559(params: &CantonEvmTransactionParams) -> anyhow::Result<Vec<u8>> {

• mpc/chain-signatures/node/src/indexer_canton/calldata.rs

  Lines 1 to 6 in 93c8e00

  	// TODO(test): golden-test build_calldata against viem's encodeFunctionData for:
  	// - ERC20 transfer/approve (static types)
  	// - Uniswap exactInputSingle with tuple arg
  	// - Functions with dynamic types (string, bytes, address[])
  	// - Empty-args view functions (totalSupply)
  	// - Invalid signature rejection, invalid hex rejection

Context: encode_unsigned_eip1559 produces the bytes that are hashed and signed for Canton bidirectional EVM transactions. Add golden tests against viem for full unsigned EIP-1559 serialization and for the calldata path used by contract calls.

Coverage to include:

• serializeTransaction with known EvmTransactionParams, verified byte-for-byte
• encodeFunctionData parity for ERC20 transfer/approve, tuple args, dynamic types, and empty-arg view functions
• invalid function signature rejection and invalid hex rejection

This absorbs #769 so the viem parity coverage is tracked in one issue.