fix: complete is_limited status handling across all views

- SubscriptionListCard: show traffic progress bar for limited subs
  in multi-tariff list (was hidden because isActive excluded limited)
- SubscriptionListCard: amber border/background for limited status
  cards (was using default neutral style, inconsistent with rest of UI)
- Subscription page: hide delete button for limited subs in
  multi-tariff mode (limited subs still have valid days remaining)
- SubscriptionPurchase: allow tariff switch for limited subs
  (was blocked by is_active-only gate in canSwitch formula)
- AdminUserDetail: include limited status in "already purchased"
  tariff filter to prevent duplicate subscription creation

src/pages/AdminUserDetail.tsx

@@ -1658,7 +1658,10 @@ export default function AdminUserDetail() {
                           .filter((tariffItem) => {
                             const purchasedIds = new Set(
                               userSubscriptions
-                                .filter((s) => s.is_active || s.status === 'trial')
+                                .filter(
+                                  (s) =>
+                                    s.is_active || s.status === 'trial' || s.status === 'limited',
+                                )
                                 .map((s) => s.tariff_id),
                             );
                             return !purchasedIds.has(tariffItem.id);