fix(ui): VK-iOS shows the pack CTA disabled with a toast, not a failed buy

Money purchases are not permitted in the VK iOS app (Apple ToS), and the backend
already refuses them (the CreateOrder VK-iOS freeze). Show the pack "Buy" muted
there and explain on tap ("purchases are not available on this platform"),
instead of letting the tap hit a 403 and a generic error toast. The storefront
still lists the packs.

ui/src/lib/i18n/en.ts

@@ -243,6 +243,7 @@ export const en = {
   'wallet.empty': 'The store is empty for now',
   'wallet.buy': 'Buy',
   'wallet.offer': 'Public offer',
+  'wallet.platformNoBuy': 'Purchases are not available on this platform',
   'wallet.gpStub': 'To buy chips, install the RuStore build.',
   'wallet.cur.RUB': '₽',
   'wallet.cur.VOTE': 'votes',