feat(trade): bypass gas check for high-value trades eligible for gasless routing

[araa47]

Summary

• Trades >= $10 USD now skip the native gas pre-check because solver-paid (gasless) routes like Relay are viable at that value
• The threshold is exported as GASLESS_MIN_TRADE_USD from trade-validation.js — one place to change it
• When gas validation does fail (trade < $10 + insufficient gas), the error message now suggests either topping up gas or increasing the trade to $10+ as alternatives

How it works

validateGasBalance accepts an optional tradeValueUsd param. If the quote's inUsdValue is >= GASLESS_MIN_TRADE_USD, the RPC balance check is skipped entirely and the function returns { hasSufficientNative: true }.

The call site in the quote handler passes response.quotes[0].inUsdValue (already populated from the API response at that point).

Test plan

• npm test passes (1479 tests)
• npm run lint passes
• New unit tests cover: bypass at exactly $10, bypass above $10, still validates below $10, error message includes gasless suggestion
• Existing integration test (quote with inUsdValue: '5.00') still correctly rejects on insufficient gas

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