feat: add LIMITED subscription status support with traffic-exhausted UX

- Add is_limited to Subscription type
- Show yellow traffic-exhausted badge on Subscription and AdminUsers pages
- SubscriptionCardExpired: amber theme with warning icon and buy-traffic CTA for limited
- Dashboard: route limited subscriptions to SubscriptionCardExpired
- Subscription page: show additional options (buy traffic) for limited subs
- Use is_limited boolean instead of status string comparison
- Add trafficLimited translations for ru, en, zh, fa
- AdminUserDetail StatusBadge: add limited yellow styling

src/locales/zh.json

@@ -163,6 +163,7 @@
     "telegramRetryFailed": "授权失败。请关闭应用后重新打开。",
     "telegramReopenHint": "如果问题持续存在，请关闭并重新打开应用",
     "telegramNotConfigured": "Telegram机器人未配置",
+    "telegramUnavailable": "Telegram登录暂时不可用",
     "authenticating": "正在验证...",
     "orOpenInApp": "或在应用中打开机器人",
     "loginFailed": "登录失败",
@@ -250,6 +251,9 @@
     "inactive": "无效",
     "trialStatus": "试用期",
     "expired": "已过期",
+    "trafficLimited": "流量已用尽",
+    "trafficLimitedTitle": "流量已达上限",
+    "trafficLimitedDescription": "您的流量已用尽。请在下方购买额外流量以继续使用VPN。",
     "expiresAt": "到期时间",
     "daysLeft": "剩余天数",
     "devices": "设备",