fix(core): use on-chain balance diff for native ETH realized amounts

[quasystaty1]

Summary

• Native ETH legs (both input and output) don't emit ERC20 Transfer events, so try_from_receipts previously fell back to the simulated strategy::Swap amounts for any native ETH token, making realized profit reflect expected values rather than actual on-chain outcomes
• Fix queries the signer's ETH balance at block N-1 and N to compute the true transferred amount:
  • ETH in: amount_in = pre_balance − post_balance − gas_cost
  • ETH out: amount_out = post_balance − pre_balance + gas_cost
• Swap::try_from_receipts is now async and takes a generic P: Provider; Trade::calculate_realized_profit constructs lightweight read-only providers from each chain's rpc_url

What a reviewer should know

• The balance-diff approach assumes the signer has exactly one transaction in the block — this holds for kuma's serial execution model (slow tx confirmed before fast tx is submitted, each on a different chain)
• The Tycho router was checked and does not emit any event when delivering native ETH to the receiver (_transferOut calls Address.sendValue with no log), so balance diff is the most practical on-chain approach without debug_traceTransaction
• ERC20 paths are unchanged — Transfer event parsing is unaffected

Test plan

• Run an ETH→token or token→ETH trade end-to-end and confirm realized_profit.slow_swap.amount_in / amount_out matches the on-chain balance change
• Confirm ERC20-only trades (no native ETH legs) are unaffected

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