Update Rates (auto-sync) — GraphQL

Refreshes every non-base currency's exchange rate from the store's configured external rate provider — the Update Rates action on the Exchange Rates screen.

• The mutation takes an empty input.
• updated is the number of exchange-rate rows present after the sync.
• If the external provider fails (missing/invalid API key, network error), the response carries an errors entry with the provider's message.

Permission: settings.exchange_rates.edit.