feat(admin): add user balance/concurrency history modal

- Add new API endpoint GET /admin/users/:id/balance-history with pagination and type filter
- Add SumPositiveBalanceByUser for calculating total recharged amount
- Create UserBalanceHistoryModal component with:
  - User info header (email, username, created_at, current balance, notes, total recharged)
  - Type filter dropdown (all/balance/admin_balance/concurrency/admin_concurrency/subscription)
  - Quick deposit/withdraw buttons
  - Paginated history list with icons and colored values
- Add instant tooltip on balance column for better UX
- Add z-index prop to BaseDialog for modal stacking control
- Update i18n translations (zh/en)

frontend/src/i18n/locales/zh.ts

@@ -883,6 +883,20 @@ export default {
       failedToDeposit: '充值失败',
       failedToWithdraw: '退款失败',
       useDepositWithdrawButtons: '请使用充值/退款按钮调整余额',
+      // 余额变动记录
+      balanceHistory: '充值记录',
+      balanceHistoryTip: '点击查看充值记录',
+      balanceHistoryTitle: '用户充值和并发变动记录',
+      noBalanceHistory: '暂无变动记录',
+      allTypes: '全部类型',
+      typeBalance: '余额（兑换码）',
+      typeAdminBalance: '余额（管理员调整）',
+      typeConcurrency: '并发（兑换码）',
+      typeAdminConcurrency: '并发（管理员调整）',
+      typeSubscription: '订阅',
+      failedToLoadBalanceHistory: '加载余额记录失败',
+      createdAt: '创建时间',
+      totalRecharged: '总充值',
       // Settings Dropdowns
       filterSettings: '筛选设置',
       columnSettings: '列设置',