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/App.tsx

@@ -26,6 +26,7 @@ import Dashboard from './pages/Dashboard';
 
 // User pages - lazy load
 const Subscription = lazy(() => import('./pages/Subscription'));
+const SubscriptionPurchase = lazy(() => import('./pages/SubscriptionPurchase'));
 const Balance = lazy(() => import('./pages/Balance'));
 const Referral = lazy(() => import('./pages/Referral'));
 const Support = lazy(() => import('./pages/Support'));
@@ -203,6 +204,16 @@ function App() {
             </ProtectedRoute>
           }
         />
+        <Route
+          path="/subscription/purchase"
+          element={
+            <ProtectedRoute>
+              <LazyPage>
+                <SubscriptionPurchase />
+              </LazyPage>
+            </ProtectedRoute>
+          }
+        />
         <Route
           path="/balance"
           element={