fix(format): convert price by exchange rate on landings and gift page

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).

src/utils/format.ts

@@ -10,27 +10,52 @@ export function formatUptime(seconds: number): string {
 }
 
 import i18next from 'i18next';
+import { currencyApi, type ExchangeRates } from '../api/currency';
 
-const LANG_CURRENCY_MAP: Record<string, { currency: string; locale: string; symbol: string }> = {
+const LANG_CURRENCY_MAP: Record<
+  string,
+  { currency: string; locale: string; symbol: string; key?: keyof ExchangeRates }
+> = {
   ru: { currency: 'RUB', locale: 'ru-RU', symbol: '₽' },
-  en: { currency: 'USD', locale: 'en-US', symbol: '$' },
-  zh: { currency: 'CNY', locale: 'zh-CN', symbol: '¥' },
-  fa: { currency: 'IRR', locale: 'fa-IR', symbol: '﷼' },
+  en: { currency: 'USD', locale: 'en-US', symbol: '$', key: 'USD' },
+  zh: { currency: 'CNY', locale: 'zh-CN', symbol: '¥', key: 'CNY' },
+  fa: { currency: 'IRR', locale: 'fa-IR', symbol: '﷼', key: 'IRR' },
 };
 
 const DEFAULT_CURRENCY = { currency: 'RUB', locale: 'ru-RU', symbol: '₽' };
 
+// Глобальный кэш курсов. Заполняется один раз из useCurrency (см. setExchangeRates ниже)
+// и используется здесь синхронно. Без него formatPrice падал в "просто замена символа",
+// что давало пользователю на лендинге `¥220` вместо реально конвертированной суммы.
+let cachedExchangeRates: ExchangeRates | null = null;
+
+export function setExchangeRates(rates: ExchangeRates | null): void {
+  cachedExchangeRates = rates;
+}
+
 export function formatPrice(kopeks: number, lang?: string): string {
   const resolvedLang = lang || i18next.language || 'ru';
   const config = LANG_CURRENCY_MAP[resolvedLang] || DEFAULT_CURRENCY;
-  const rubles = kopeks / 100;
+  let amount = kopeks / 100;
+
+  // Конвертация по курсу для не-рублёвых локалей. Без rates fallback на сырую сумму
+  // (поведение до фикса), чтобы первый рендер до загрузки курсов не отдавал NaN.
+  if (config.key && cachedExchangeRates) {
+    amount = currencyApi.convertFromRub(amount, config.key, cachedExchangeRates);
+  }
+
+  // Для IRR суммы большие — без дробной части.
+  const maximumFractionDigits = config.currency === 'IRR' ? 0 : 2;
+
   try {
     return new Intl.NumberFormat(config.locale, {
       style: 'currency',
       currency: config.currency,
-      maximumFractionDigits: 0,
-    }).format(rubles);
+      maximumFractionDigits,
+    }).format(amount);
   } catch {
-    return `${Math.round(rubles)} ${config.symbol}`;
+    const rounded =
+      maximumFractionDigits === 0 ? Math.round(amount) : Math.round(amount * 100) / 100;
+    return `${rounded} ${config.symbol}`;
   }
 }