v1.0.39

Added a canonical institution ID guide for China USD LOCAL_BANK_TRANSFER accounts, including all supported institution IDs

Documented institution_id as required when creating an external account or adding a bank account to a recipient, with links to
the new guide

Standardized fiat rail identifiers—including US_ACH, US_FEDWIRE, US_RTP, SWIFT, LOCAL_BANK_TRANSFER, and CHATS—across
the guides and API reference