feat: 账号管理新增使用统计功能

- 新增账号统计弹窗，展示30天使用数据
- 显示总费用、请求数、日均费用、日均请求等汇总指标
- 显示今日概览、最高费用日、最高请求日
- 包含费用与请求趋势图（双Y轴）
- 复用模型分布图组件展示模型使用分布
- 显示实际扣费和标准计费（标准计费以较淡颜色显示）

frontend/src/i18n/locales/en.ts

@@ -825,6 +825,39 @@ export default {
       selectTestModel: 'Select Test Model',
       testModel: 'claude-sonnet-4-5-20250929',
       testPrompt: 'Prompt: "hi"',
+      // Stats Modal
+      viewStats: 'View Stats',
+      usageStatistics: 'Usage Statistics',
+      last30DaysUsage: 'Last 30 days usage statistics (based on actual usage days)',
+      stats: {
+        totalCost: '30-Day Total Cost',
+        accumulatedCost: 'Accumulated cost',
+        standardCost: 'Standard',
+        totalRequests: '30-Day Total Requests',
+        totalCalls: 'Total API calls',
+        avgDailyCost: 'Daily Avg Cost',
+        basedOnActualDays: 'Based on {days} actual usage days',
+        avgDailyRequests: 'Daily Avg Requests',
+        avgDailyUsage: 'Average daily usage',
+        todayOverview: 'Today Overview',
+        cost: 'Cost',
+        requests: 'Requests',
+        highestCostDay: 'Highest Cost Day',
+        highestRequestDay: 'Highest Request Day',
+        date: 'Date',
+        accumulatedTokens: 'Accumulated Tokens',
+        totalTokens: '30-Day Total',
+        dailyAvgTokens: 'Daily Average',
+        performance: 'Performance',
+        avgResponseTime: 'Avg Response',
+        daysActive: 'Days Active',
+        recentActivity: 'Recent Activity',
+        todayRequests: 'Today Requests',
+        todayTokens: 'Today Tokens',
+        todayCost: 'Today Cost',
+        usageTrend: '30-Day Cost & Request Trend',
+        noData: 'No usage data available for this account',
+      },
     },
 
     // Proxies

frontend/src/i18n/locales/zh.ts

@@ -918,6 +918,39 @@ export default {
       selectTestModel: '选择测试模型',
       testModel: 'claude-sonnet-4-5-20250929',
       testPrompt: '提示词："hi"',
+      // Stats Modal
+      viewStats: '查看统计',
+      usageStatistics: '使用统计',
+      last30DaysUsage: '近30天使用统计（日均基于实际使用天数）',
+      stats: {
+        totalCost: '30天总费用',
+        accumulatedCost: '累计成本',
+        standardCost: '标准计费',
+        totalRequests: '30天总请求',
+        totalCalls: '累计调用次数',
+        avgDailyCost: '日均费用',
+        basedOnActualDays: '基于 {days} 天实际使用',
+        avgDailyRequests: '日均请求',
+        avgDailyUsage: '平均每日调用',
+        todayOverview: '今日概览',
+        cost: '费用',
+        requests: '请求',
+        highestCostDay: '最高费用日',
+        highestRequestDay: '最高请求日',
+        date: '日期',
+        accumulatedTokens: '累计 Token',
+        totalTokens: '30天总计',
+        dailyAvgTokens: '日均 Token',
+        performance: '性能',
+        avgResponseTime: '平均响应',
+        daysActive: '活跃天数',
+        recentActivity: '最近统计',
+        todayRequests: '今日请求',
+        todayTokens: '今日 Token',
+        todayCost: '今日费用',
+        usageTrend: '30天费用与请求趋势',
+        noData: '该账号暂无使用数据',
+      },
     },
 
     // Proxies Management