fix(group): harden peak-rate config handling and label peak windows with server timezone

Follow-up fixes to #3569 based on code audit:

- Expose server_timezone / server_utc_offset in public settings (and the
  __APP_CONFIG__ injection payload) and label every peak-window display
  with the server UTC offset, so users don't misread the billing window
  as browser-local time
- Unify CreateGroup/UpdateGroup peak-config sanitization via a single
  NormalizePeakRateConfig chokepoint: non-subscription groups always get
  peak fields cleared; unparseable window strings and negative
  multipliers are scrubbed when peak is disabled
- Replace hot-path time.Parse in PeakMultiplierAt with a manual HH:MM
  parser (accept set verified byte-for-byte identical to
  time.Parse("15:04") by exhaustive fuzzing) and reuse it in validation
- Revert the zero-behavior CalculateCost indirection churn in
  billing_service/gateway_service introduced by #3569
- Remove dead GetGroupPlatformMap and the duplicate deref helper in the
  admin handler package
- Share frontend peak formatting via utils/peak-rate.ts, unify the ×N
  label format, and move hardcoded Chinese tooltips to i18n keys

frontend/src/components/channels/AvailableChannelsTable.vue

@@ -178,6 +178,8 @@ import SupportedModelChip from './SupportedModelChip.vue'
 import type { UserAvailableChannel, UserAvailableGroup, UserChannelPlatformSection } from '@/api/channels'
 import type { GroupPlatform, SubscriptionType } from '@/types'
 import { platformBadgeClass } from '@/utils/platformColors'
+import { useAppStore } from '@/stores/app'
+import { hasPeakRate as groupHasPeakRate, formatPeakRateWindow, serverTimezoneLabel } from '@/utils/peak-rate'
 
 const props = defineProps<{
   columns: {
@@ -211,15 +213,17 @@ function publicGroups(section: UserChannelPlatformSection): UserAvailableGroup[]
   return section.groups.filter((g) => !g.is_exclusive)
 }
 
+const appStore = useAppStore()
+
 function hasPeakRate(group: UserAvailableGroup): boolean {
-  return Boolean(group.peak_rate_enabled && group.peak_start && group.peak_end)
+  return groupHasPeakRate(group)
 }
 
 function peakRateLabel(group: UserAvailableGroup): string {
-  return `${group.peak_start}-${group.peak_end} ${group.peak_rate_multiplier}x`
+  return formatPeakRateWindow(group, serverTimezoneLabel(appStore.cachedPublicSettings?.server_utc_offset))
 }
 
 function peakRateTitle(group: UserAvailableGroup): string {
-  return `高峰倍率：${group.peak_start}-${group.peak_end} ${group.peak_rate_multiplier}x；token 计费的图片 token 同样适用，图片按次计费不受高峰影响`
+  return t('common.peakRateTooltip', { window: peakRateLabel(group) }) + t('common.peakRateImageNote')
 }
 </script>

frontend/src/components/common/GroupBadge.vue

@@ -30,6 +30,8 @@
 import { computed } from 'vue'
 import { useI18n } from 'vue-i18n'
 import type { SubscriptionType, GroupPlatform } from '@/types'
+import { useAppStore } from '@/stores/app'
+import { formatPeakRateWindow, serverTimezoneLabel } from '@/utils/peak-rate'
 import PlatformIcon from './PlatformIcon.vue'
 
 interface Props {
@@ -75,16 +77,26 @@ const hasCustomRate = computed(() => {
   )
 })
 
+const appStore = useAppStore()
+
 const hasPeakRate = computed(() => {
   return Boolean(props.showRate && props.peakRateEnabled && props.peakStart && props.peakEnd)
 })
 
 const peakRateText = computed(() => {
-  return `${props.peakStart}-${props.peakEnd} ×${props.peakRateMultiplier ?? 1}`
+  return formatPeakRateWindow(
+    {
+      peak_rate_enabled: props.peakRateEnabled,
+      peak_start: props.peakStart,
+      peak_end: props.peakEnd,
+      peak_rate_multiplier: props.peakRateMultiplier
+    },
+    serverTimezoneLabel(appStore.cachedPublicSettings?.server_utc_offset)
+  )
 })
 
 const peakRateTitle = computed(() => {
-  return `高峰倍率：${peakRateText.value}`
+  return t('common.peakRateTooltip', { window: peakRateText.value })
 })
 
 // 是否显示右侧标签

frontend/src/components/common/GroupOptionItem.vue

@@ -63,6 +63,8 @@ import { computed } from 'vue'
 import { useI18n } from 'vue-i18n'
 import GroupBadge from './GroupBadge.vue'
 import type { SubscriptionType, GroupPlatform } from '@/types'
+import { useAppStore } from '@/stores/app'
+import { formatPeakRateWindow, serverTimezoneLabel } from '@/utils/peak-rate'
 
 const { t } = useI18n()
 
@@ -99,16 +101,26 @@ const hasCustomRate = computed(() => {
   )
 })
 
+const appStore = useAppStore()
+
 const hasPeakRate = computed(() => {
   return Boolean(props.peakRateEnabled && props.peakStart && props.peakEnd)
 })
 
 const peakRateText = computed(() => {
-  return `${props.peakStart}-${props.peakEnd} ×${props.peakRateMultiplier ?? 1}`
+  return formatPeakRateWindow(
+    {
+      peak_rate_enabled: props.peakRateEnabled,
+      peak_start: props.peakStart,
+      peak_end: props.peakEnd,
+      peak_rate_multiplier: props.peakRateMultiplier
+    },
+    serverTimezoneLabel(appStore.cachedPublicSettings?.server_utc_offset)
+  )
 })
 
 const peakRateTitle = computed(() => {
-  return `高峰倍率：${peakRateText.value}`
+  return t('common.peakRateTooltip', { window: peakRateText.value })
 })
 
 // Rate pill color matches platform badge color

frontend/src/components/payment/SubscriptionPlanCard.vue

@@ -103,6 +103,8 @@ import { computed } from 'vue'
 import { useI18n } from 'vue-i18n'
 import type { SubscriptionPlan } from '@/types/payment'
 import type { UserSubscription } from '@/types'
+import { useAppStore } from '@/stores/app'
+import { hasPeakRate as groupHasPeakRate, formatPeakRateWindow, serverTimezoneLabel } from '@/utils/peak-rate'
 import {
   platformAccentBarClass,
   platformBadgeLightClass,
@@ -144,12 +146,12 @@ const rateDisplay = computed(() => {
   return `×${Number(rate.toPrecision(10))}`
 })
 
-const hasPeakRate = computed(() => {
-  return Boolean(props.plan.peak_rate_enabled && props.plan.peak_start && props.plan.peak_end)
-})
+const appStore = useAppStore()
+
+const hasPeakRate = computed(() => groupHasPeakRate(props.plan))
 
 const peakRateDisplay = computed(() => {
-  return `${props.plan.peak_start}-${props.plan.peak_end} ×${props.plan.peak_rate_multiplier ?? 1}`
+  return formatPeakRateWindow(props.plan, serverTimezoneLabel(appStore.cachedPublicSettings?.server_utc_offset))
 })
 
 const MODEL_SCOPE_LABELS: Record<string, string> = {

frontend/src/components/payment/__tests__/SubscriptionPlanCard.spec.ts

@@ -1,5 +1,6 @@
 import { mount } from "@vue/test-utils";
 import { describe, expect, it } from "vitest";
+import { createPinia } from "pinia";
 import { createI18n } from "vue-i18n";
 import SubscriptionPlanCard from "../SubscriptionPlanCard.vue";
 
@@ -42,7 +43,7 @@ const mountPlanCard = (groupPlatform: string) =>
         is_active: true,
       },
     },
-    global: { plugins: [i18n] },
+    global: { plugins: [i18n, createPinia()] },
   });
 
 describe("SubscriptionPlanCard", () => {

frontend/src/i18n/locales/en.ts

@@ -252,6 +252,8 @@ export default {
     loading: 'Loading...',
     submitting: 'Submitting...',
     justNow: 'just now',
+    peakRateTooltip: 'Peak rate: {window}',
+    peakRateImageNote: '; image tokens billed as tokens are also affected, per-image billing is unaffected',
     save: 'Save',
     saved: 'Saved successfully',
     deleted: 'Deleted successfully',

frontend/src/i18n/locales/zh.ts

@@ -252,6 +252,8 @@ export default {
     loading: '加载中...',
     submitting: '提交中...',
     justNow: '刚刚',
+    peakRateTooltip: '高峰倍率：{window}',
+    peakRateImageNote: '；token 计费的图片 token 同样适用，图片按次计费不受高峰影响',
     save: '保存',
     saved: '保存成功',
     deleted: '删除成功',

frontend/src/types/index.ts

@@ -227,6 +227,10 @@ export interface PublicSettings {
   google_oauth_enabled: boolean
   backend_mode_enabled: boolean
   version: string
+  // 服务器全局时区（IANA 名称与当前 UTC 偏移），高峰时段等服务端本地时间窗口的展示标注用；
+  // 可选：注入的 __APP_CONFIG__ 旧缓存可能缺失
+  server_timezone?: string
+  server_utc_offset?: string
   balance_low_notify_enabled: boolean
   account_quota_notify_enabled: boolean
   balance_low_notify_threshold: number

frontend/src/utils/peak-rate.ts

@@ -0,0 +1,33 @@
+/**
+ * 高峰时段倍率的共享展示逻辑。
+ *
+ * 高峰窗口由后端按服务器全局时区判定（Group.PeakMultiplierAt），
+ * 前端展示必须带上服务器时区标注（来自公共设置 server_utc_offset），
+ * 避免用户按浏览器本地时间误读计费窗口。
+ */
+
+export interface PeakRateFields {
+  peak_rate_enabled?: boolean
+  peak_start?: string
+  peak_end?: string
+  peak_rate_multiplier?: number
+}
+
+export function hasPeakRate(fields?: PeakRateFields | null): boolean {
+  return Boolean(fields?.peak_rate_enabled && fields.peak_start && fields.peak_end)
+}
+
+/** "+08:00" → "UTC+08:00"；旧缓存无该字段时返回空串，调用方降级为不带时区标注 */
+export function serverTimezoneLabel(utcOffset?: string | null): string {
+  return utcOffset ? `UTC${utcOffset}` : ''
+}
+
+/** "14:00-18:00 ×2 (UTC+08:00)"，tzLabel 为空时省略括号部分 */
+export function formatPeakRateWindow(
+  fields: PeakRateFields | null | undefined,
+  tzLabel?: string
+): string {
+  if (!hasPeakRate(fields) || !fields) return ''
+  const base = `${fields.peak_start}-${fields.peak_end} ×${fields.peak_rate_multiplier ?? 1}`
+  return tzLabel ? `${base} (${tzLabel})` : base
+}

frontend/src/views/user/PaymentView.vue

@@ -262,6 +262,7 @@ import { useAppStore } from '@/stores'
 import { paymentAPI } from '@/api/payment'
 import { extractApiErrorMessage, extractI18nErrorMessage } from '@/utils/apiError'
 import { isMobileDevice } from '@/utils/device'
+import { hasPeakRate, formatPeakRateWindow, serverTimezoneLabel, type PeakRateFields } from '@/utils/peak-rate'
 import type { SubscriptionPlan, CheckoutInfoResponse, CreateOrderResult, OrderType } from '@/types/payment'
 import AppLayout from '@/components/layout/AppLayout.vue'
 import AmountInput from '@/components/payment/AmountInput.vue'
@@ -304,14 +305,12 @@ function getDaysRemaining(expiresAt: string): number {
   return Math.max(0, Math.ceil(diff / (1000 * 60 * 60 * 24)))
 }
 
-function subscriptionHasPeakRate(sub: { group?: { peak_rate_enabled?: boolean; peak_start?: string; peak_end?: string } | null }): boolean {
-  const group = sub.group
-  return Boolean(group?.peak_rate_enabled && group.peak_start && group.peak_end)
+function subscriptionHasPeakRate(sub: { group?: PeakRateFields | null }): boolean {
+  return hasPeakRate(sub.group)
 }
 
-function subscriptionPeakRateLabel(sub: { group?: { peak_start?: string; peak_end?: string; peak_rate_multiplier?: number } | null }): string {
-  const group = sub.group
-  return `${group?.peak_start}-${group?.peak_end} ×${group?.peak_rate_multiplier ?? 1}`
+function subscriptionPeakRateLabel(sub: { group?: PeakRateFields | null }): string {
+  return formatPeakRateWindow(sub.group, serverTimezoneLabel(appStore.cachedPublicSettings?.server_utc_offset))
 }
 
 const loading = ref(true)
@@ -713,11 +712,11 @@ const planValiditySuffix = computed(() => {
 })
 
 function planHasPeakRate(plan: SubscriptionPlan): boolean {
-  return Boolean(plan.peak_rate_enabled && plan.peak_start && plan.peak_end)
+  return hasPeakRate(plan)
 }
 
 function planPeakRateLabel(plan: SubscriptionPlan): string {
-  return `${plan.peak_start}-${plan.peak_end} ×${plan.peak_rate_multiplier ?? 1}`
+  return formatPeakRateWindow(plan, serverTimezoneLabel(appStore.cachedPublicSettings?.server_utc_offset))
 }
 
 function selectPlan(plan: SubscriptionPlan) {

frontend/src/views/user/SubscriptionsView.vue

@@ -257,6 +257,7 @@ import type { UserSubscription } from '@/types'
 import AppLayout from '@/components/layout/AppLayout.vue'
 import Icon from '@/components/icons/Icon.vue'
 import { formatDateOnly } from '@/utils/format'
+import { hasPeakRate, formatPeakRateWindow, serverTimezoneLabel } from '@/utils/peak-rate'
 import { platformBorderClass, platformBadgeClass, platformButtonClass, platformLabel } from '@/utils/platformColors'
 import { getRemainingDurationParts, isOneTimeDailyQuota, type RemainingDurationParts } from '@/utils/subscriptionQuota'
 
@@ -278,13 +279,11 @@ const subscriptions = ref<UserSubscription[]>([])
 const loading = ref(true)
 
 function subscriptionHasPeakRate(subscription: UserSubscription): boolean {
-  const group = subscription.group
-  return Boolean(group?.peak_rate_enabled && group.peak_start && group.peak_end)
+  return hasPeakRate(subscription.group)
 }
 
 function subscriptionPeakRateLabel(subscription: UserSubscription): string {
-  const group = subscription.group
-  return `${group?.peak_start}-${group?.peak_end} ×${group?.peak_rate_multiplier ?? 1}`
+  return formatPeakRateWindow(subscription.group, serverTimezoneLabel(appStore.cachedPublicSettings?.server_utc_offset))
 }
 
 async function loadSubscriptions() {