feat: add Apple IAP (apple_iap) payment method support

Add apple_iap across all payment surfaces: method label, icon (Apple
logo SVG), admin settings tree (APPLE_IAP category), and all four
locale files (en, ru, fa, zh) with payment description + tree label.

src/constants/paymentMethods.ts

@@ -18,5 +18,6 @@ export const METHOD_LABELS: Record<string, string> = {
   paypear: 'PayPear',
   rollypay: 'RollyPay',
   aurapay: 'AuraPay',
+  apple_iap: 'Apple In-App Purchase',
   manual: 'Ручное пополнение',
 };