feat: separate renewal and purchase flows in multi-tariff mode

Renewal flow (per-subscription):
- New /subscriptions/:id/renew page showing only period options for
  the specific tariff with balance display and renew button
- PurchaseCTAButton links to /renew in multi-tariff mode

Purchase flow (new tariffs only):
- Hide already purchased tariffs (is_purchased flag from backend)
- Fallback UI when all tariffs are owned
- Types: added is_purchased, all_tariffs_purchased fields

src/App.tsx

@@ -44,6 +44,7 @@ const Connection = lazy(() => import('./pages/Connection'));
 const ConnectionQR = lazy(() => import('./pages/ConnectionQR'));
 const QuickPurchase = lazy(() => import('./pages/QuickPurchase'));
 const PurchaseSuccess = lazy(() => import('./pages/PurchaseSuccess'));
+const RenewSubscription = lazy(() => import('./pages/RenewSubscription'));
 const AutoLogin = lazy(() => import('./pages/AutoLogin'));
 const TopUpMethodSelect = lazy(() => import('./pages/TopUpMethodSelect'));
 const TopUpAmount = lazy(() => import('./pages/TopUpAmount'));
@@ -284,6 +285,16 @@ function App() {
             </ProtectedRoute>
           }
         />
+        <Route
+          path="/subscriptions/:subscriptionId/renew"
+          element={
+            <ProtectedRoute>
+              <LazyPage>
+                <RenewSubscription />
+              </LazyPage>
+            </ProtectedRoute>
+          }
+        />
         {/* Legacy redirects for backward compatibility */}
         <Route path="/subscription/:subscriptionId" element={<LegacySubscriptionRedirect />} />
         <Route