fix: read basic-order ERC20 preflight from API parameters

[Mabolla]

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Summary

Fixes ERC20 fulfillment preflight for basic-order responses by reading the API's actual inputData.parameters shape.

Root cause

The fulfillment API returns basic-order data under inputData.parameters, but getErc20Payment() and getFulfillerConduitKey() were still looking for basicOrderParameters.

As a result, ERC20 basic listings could skip the payment/allowance preflight because the helper returned no payment data. The existing unit fixture used the same stale field name, so it did not cover the production wire shape.

Changes

• Read basic-order payment data from inputData.parameters.
• Read the basic-order fulfiller conduit key from inputData.parameters.
• Keep basicOrderParameters as a compatibility fallback.
• Update the regression fixture to match the API wire shape.

Validation

• test/orders/erc20Fulfillment.spec.ts: 30/30 passed.
• Full unit suite: 945/945 passed across 41 test files.
• Targeted Biome check passes for the changed files.