fix(usage): 用户使用记录不下发账号计费倍率

- 将 usage log DTO 拆分为用户/管理员两类
- 用户接口不返回 account_rate_multiplier/ip_address/account
- 管理员接口保留管理员字段
- 补充契约测试防止回归

frontend/src/components/admin/usage/UsageTable.vue

@@ -239,7 +239,7 @@ import { formatDateTime } from '@/utils/format'
 import DataTable from '@/components/common/DataTable.vue'
 import EmptyState from '@/components/common/EmptyState.vue'
 import Icon from '@/components/icons/Icon.vue'
-import type { UsageLog } from '@/types'
+import type { AdminUsageLog } from '@/types'
 
 defineProps(['data', 'loading'])
 const { t } = useI18n()
@@ -247,12 +247,12 @@ const { t } = useI18n()
 // Tooltip state - cost
 const tooltipVisible = ref(false)
 const tooltipPosition = ref({ x: 0, y: 0 })
-const tooltipData = ref<UsageLog | null>(null)
+const tooltipData = ref<AdminUsageLog | null>(null)
 
 // Tooltip state - token
 const tokenTooltipVisible = ref(false)
 const tokenTooltipPosition = ref({ x: 0, y: 0 })
-const tokenTooltipData = ref<UsageLog | null>(null)
+const tokenTooltipData = ref<AdminUsageLog | null>(null)
 
 const cols = computed(() => [
   { key: 'user', label: t('admin.usage.user'), sortable: false },
@@ -296,7 +296,7 @@ const formatDuration = (ms: number | null | undefined): string => {
 }
 
 // Cost tooltip functions
-const showTooltip = (event: MouseEvent, row: UsageLog) => {
+const showTooltip = (event: MouseEvent, row: AdminUsageLog) => {
   const target = event.currentTarget as HTMLElement
   const rect = target.getBoundingClientRect()
   tooltipData.value = row
@@ -311,7 +311,7 @@ const hideTooltip = () => {
 }
 
 // Token tooltip functions
-const showTokenTooltip = (event: MouseEvent, row: UsageLog) => {
+const showTokenTooltip = (event: MouseEvent, row: AdminUsageLog) => {
   const target = event.currentTarget as HTMLElement
   const rect = target.getBoundingClientRect()
   tokenTooltipData.value = row