formatPrice from utils/format.ts only swapped the currency symbol
(220 ₽ -> ¥220) without converting the underlying amount, because it
had no source of exchange rates and the landing/gift pages never called
the useCurrency hook that knew how to fetch them.
- Add a module-level rates cache in utils/format with setExchangeRates
setter. formatPrice now converts kopeks/100 from RUB to the target
currency via currencyApi.convertFromRub when rates are cached.
- useCurrency pushes its loaded rates into that cache so any subsequent
formatPrice call benefits, including subcomponents that cannot easily
receive a prop.
- Call useCurrency in QuickPurchase, GiftSubscription, and
AdminLandingEditor — the only entry points whose subcomponents still
use the synchronous formatPrice (everything else already routes
through useCurrency.formatAmount).
For RU locale behavior is unchanged. For EN/ZH/FA the amount is now
divided by the per-currency rate and formatted via Intl.NumberFormat
with 2 fraction digits (0 for IRR since amounts are large).
