Idempotent locate creation with Idempotency-Key

Trading API

Adds support for safe retries when creating locates using the Idempotency-Key header on POST /v1/locates. Reusing a key returns the original result, and a new idempotency_key_conflict value on the LocateError schema signals when a key is reused with a different request payload.

Affected Endpoints

• POST /v1/locates