fix: improve tariff delete button visibility

- Added visual styling for disabled delete button (when tariff has
  active subscriptions)
- Added tooltip explaining why delete is disabled
- Added i18n translations for cannotDeleteHasSubscriptions

src/locales/fa.json

@@ -989,6 +989,7 @@
       "deactivate": "غیرفعال‌سازی",
       "toggleTrial": "تغییر آزمایشی",
       "delete": "حذف",
+      "cannotDeleteHasSubscriptions": "حذف ممکن نیست: اشتراک‌های فعال وجود دارد",
       "confirmDelete": "تعرفه حذف شود؟",
       "confirmDeleteText": "این عمل قابل بازگشت نیست. تعرفه برای همیشه حذف می‌شود.",
       "days": "روز",