refactor: extract purchase/renewal flow to separate page

Move ~1900 lines of purchase/renewal logic from Subscription.tsx into
a new SubscriptionPurchase.tsx page at /subscription/purchase.

- Create SubscriptionPurchase.tsx with tariffs grid, classic mode wizard,
  switch preview modal, and promo handling
- Create PurchaseCTAButton.tsx with animated gradient border, state-aware
  colors and context-aware text
- Create subscriptionHelpers.ts with shared utilities
- Add CopyIcon to shared icons module
- Register /subscription/purchase route with lazy loading
- Update SubscriptionCardExpired and PromoOffersSection navigators
- Add CTA translation keys to ru.json and en.json
- Remove all scrollToExtend references

src/components/dashboard/SubscriptionCardExpired.tsx

@@ -139,8 +139,7 @@ export default function SubscriptionCardExpired({ subscription }: SubscriptionCa
       {/* Action buttons */}
       <div className="flex gap-2.5">
         <Link
-          to="/subscription"
-          state={{ scrollToExtend: true }}
+          to="/subscription/purchase"
           className="flex flex-1 items-center justify-center rounded-[14px] py-3.5 text-[15px] font-semibold tracking-tight text-white transition-all duration-300"
           style={{
             background: 'linear-gradient(135deg, #FF3B5C, #FF6B35)',