fix: support transaction overrides in fulfillOrders

[aproskill81]

Motivation

fulfillOrders did not expose transaction overrides even though fulfillOrder already supports them. This prevented callers from setting transaction-level fields such as gasLimit, nonce, or fee overrides when fulfilling multiple orders.

Solution

Add overrides to the fulfillOrders input and pass it through to fulfillAvailableOrders.

The final transaction overrides preserve the SDK-calculated native token value while forwarding caller-provided fields. Added coverage that verifies a provided gasLimit is included in the built fulfillment transaction.