feat: add traffic abuse risk assessment with color gradation

Add threshold inputs (total GB/day, per-node GB/day) to admin traffic
usage page. When set, rows get background color gradation (green to red)
and node cells get text color (blue to red) based on threshold ratios.
Conditional Risk column shows composite risk badge with level indicator.
7 i18n keys added across all 4 locales (ru, en, zh, fa).

src/locales/en.json

@@ -815,7 +815,14 @@
       "statusDisabled": "Disabled",
       "customDates": "Custom dates",
       "dateFrom": "From",
-      "dateTo": "To"
+      "dateTo": "To",
+      "totalThreshold": "Total GB/d",
+      "nodeThreshold": "Node GB/d",
+      "risk": "Risk",
+      "riskLow": "Low",
+      "riskMedium": "Medium",
+      "riskHigh": "High",
+      "riskCritical": "Critical"
     },
     "emailTemplates": {
       "title": "Email Templates",

src/locales/fa.json

@@ -696,7 +696,14 @@
       "statusDisabled": "غیرفعال",
       "customDates": "تاریخ دلخواه",
       "dateFrom": "از",
-      "dateTo": "تا"
+      "dateTo": "تا",
+      "totalThreshold": "کل GB/روز",
+      "nodeThreshold": "نود GB/روز",
+      "risk": "ریسک",
+      "riskLow": "کم",
+      "riskMedium": "متوسط",
+      "riskHigh": "بالا",
+      "riskCritical": "بحرانی"
     },
     "emailTemplates": {
       "title": "قالب‌های ایمیل",

src/locales/ru.json

@@ -836,7 +836,14 @@
       "statusDisabled": "Отключена",
       "customDates": "Выбрать даты",
       "dateFrom": "От",
-      "dateTo": "До"
+      "dateTo": "До",
+      "totalThreshold": "Всего ГБ/д",
+      "nodeThreshold": "Нода ГБ/д",
+      "risk": "Риск",
+      "riskLow": "Низкий",
+      "riskMedium": "Средний",
+      "riskHigh": "Высокий",
+      "riskCritical": "Критический"
     },
     "emailTemplates": {
       "title": "Email-шаблоны",

src/locales/zh.json

@@ -696,7 +696,14 @@
       "statusDisabled": "已禁用",
       "customDates": "自定义日期",
       "dateFrom": "从",
-      "dateTo": "到"
+      "dateTo": "到",
+      "totalThreshold": "总流量GB/天",
+      "nodeThreshold": "节点GB/天",
+      "risk": "风险",
+      "riskLow": "低",
+      "riskMedium": "中",
+      "riskHigh": "高",
+      "riskCritical": "严重"
     },
     "paymentMethods": {
       "title": "支付方法",