Added

Quotations: `base_currency` accepts `USDC` and `USDT`

What's new/v1/quotations accepts USDC and USDT as base_currency, in addition to USD. You can now quote against stablecoin-funded flows directly.

The /v1/quotations reference is also now visible in the navigation (was previously hidden).

Impact — Additive enum values. Existing requests using base_currency: "USD" are unchanged.

ReferencePOST /v1/quotations