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/en.json

@@ -1215,6 +1215,7 @@
       "deactivate": "Deactivate",
       "toggleTrial": "Toggle Trial",
       "delete": "Delete",
+      "cannotDeleteHasSubscriptions": "Cannot delete: has active subscriptions",
       "confirmDelete": "Delete tariff?",
       "confirmDeleteText": "This action cannot be undone. The tariff will be permanently deleted.",
       "days": "days",

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",

src/locales/ru.json

@@ -1725,6 +1725,7 @@
       "deactivate": "Деактивировать",
       "toggleTrial": "Переключить триал",
       "delete": "Удалить",
+      "cannotDeleteHasSubscriptions": "Нельзя удалить: есть активные подписки",
       "confirmDelete": "Удалить тариф?",
       "confirmDeleteText": "Это действие нельзя отменить. Тариф будет удален навсегда.",
       "days": "дней",

src/locales/zh.json

@@ -1027,6 +1027,7 @@
       "deactivate": "停用",
       "toggleTrial": "切换试用",
       "delete": "删除",
+      "cannotDeleteHasSubscriptions": "无法删除：有活跃订阅",
       "confirmDelete": "删除套餐？",
       "confirmDeleteText": "此操作不可撤销。套餐将被永久删除。",
       "days": "天",

src/pages/AdminTariffs.tsx

@@ -205,8 +205,16 @@ export default function AdminTariffs() {
                   {/* Delete */}
                   <button
                     onClick={() => setDeleteConfirm(tariff.id)}
-                    className="rounded-lg bg-dark-700 p-2 text-dark-300 transition-colors hover:bg-error-500/20 hover:text-error-400"
-                    title={t('admin.tariffs.delete')}
+                    className={`rounded-lg p-2 transition-colors ${
+                      tariff.subscriptions_count > 0
+                        ? 'cursor-not-allowed bg-dark-700/50 text-dark-500'
+                        : 'bg-dark-700 text-dark-300 hover:bg-error-500/20 hover:text-error-400'
+                    }`}
+                    title={
+                      tariff.subscriptions_count > 0
+                        ? t('admin.tariffs.cannotDeleteHasSubscriptions')
+                        : t('admin.tariffs.delete')
+                    }
                     disabled={tariff.subscriptions_count > 0}
                   >
                     <TrashIcon />