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)

backend/internal/server/routes/admin.go

@@ -172,6 +172,7 @@ func registerUserManagementRoutes(admin *gin.RouterGroup, h *handler.Handlers) {
 		users.POST("/:id/balance", h.Admin.User.UpdateBalance)
 		users.GET("/:id/api-keys", h.Admin.User.GetUserAPIKeys)
 		users.GET("/:id/usage", h.Admin.User.GetUserUsage)
+		users.GET("/:id/balance-history", h.Admin.User.GetBalanceHistory)
 
 		// User attribute values
 		users.GET("/:id/attributes", h.Admin.UserAttribute.GetUserAttributes)