fix: address audit findings across websearch, notify, and channel pricing

Backend fixes:
- Fix balance notify ignoring percentage threshold type (was treating
  percentage value as fixed USD amount)
- Remove dead code parseJSONStringArray
- Add ImageOutputTokens to tryModelFilePricing calculation
- Unify zero-value check: cost == 0 → cost <= 0 in calculateTokenStatsCost
- Use MarshalNotifyEmails instead of json.Marshal for consistency
- Rename quotaDim.oldUsed → currentUsed for clarity
- Extract HTML email templates to const variables (function ≤30 lines)

Test fixes:
- Rewrite account_websearch_test.go for GetWebSearchEmulationMode tri-state
- Add 6 tryModelFilePricing test cases

Frontend fixes:
- Replace hardcoded '未命名' with i18n key
- Extract getBillingModeLabel/getBillingModeBadgeClass to shared utils
- Replace inline type with imported NotifyEmailEntry
- Pass platform to AccountStats pricing rules via inferRulePlatform()
- Add billing mode constants (BILLING_MODE_TOKEN/PER_REQUEST/IMAGE)

frontend/src/views/admin/ChannelsView.vue

@@ -980,26 +980,38 @@ function clearAllRuleAccountSearchState() {
   showRuleAccountDropdown.value = {}
 }
 
+function inferRulePlatform(groupIds: number[]): string {
+  const platforms = new Set<string>()
+  for (const gid of groupIds) {
+    const group = allGroups.value.find(g => g.id === gid)
+    if (group) platforms.add(group.platform)
+  }
+  return platforms.size === 1 ? [...platforms][0] : ''
+}
+
 function accountStatsRulesToAPI(): AccountStatsPricingRule[] {
-  return form.account_stats_pricing_rules.map(rule => ({
-    name: rule.name,
-    group_ids: rule.group_ids,
-    account_ids: rule.account_ids,
-    pricing: rule.pricing
-      .filter(p => p.models.length > 0)
-      .map(p => ({
-        platform: '',
-        models: p.models,
-        billing_mode: p.billing_mode,
-        input_price: mTokToPerToken(p.input_price),
-        output_price: mTokToPerToken(p.output_price),
-        cache_write_price: mTokToPerToken(p.cache_write_price),
-        cache_read_price: mTokToPerToken(p.cache_read_price),
-        image_output_price: mTokToPerToken(p.image_output_price),
-        per_request_price: p.per_request_price != null && p.per_request_price !== '' ? Number(p.per_request_price) : null,
-        intervals: formIntervalsToAPI(p.intervals || [])
-      }))
-  }))
+  return form.account_stats_pricing_rules.map(rule => {
+    const platform = inferRulePlatform(rule.group_ids)
+    return {
+      name: rule.name,
+      group_ids: rule.group_ids,
+      account_ids: rule.account_ids,
+      pricing: rule.pricing
+        .filter(p => p.models.length > 0)
+        .map(p => ({
+          platform,
+          models: p.models,
+          billing_mode: p.billing_mode,
+          input_price: mTokToPerToken(p.input_price),
+          output_price: mTokToPerToken(p.output_price),
+          cache_write_price: mTokToPerToken(p.cache_write_price),
+          cache_read_price: mTokToPerToken(p.cache_read_price),
+          image_output_price: mTokToPerToken(p.image_output_price),
+          per_request_price: p.per_request_price != null && p.per_request_price !== '' ? Number(p.per_request_price) : null,
+          intervals: formIntervalsToAPI(p.intervals || [])
+        }))
+    }
+  })
 }
 
 // ── Form ↔ API conversion ──
@@ -1329,7 +1341,7 @@ async function handleSubmit() {
       const intervalErr = validateIntervals(entry.intervals)
       if (intervalErr) {
         const platformLabel = t('admin.groups.platforms.' + section.platform, section.platform)
-        const modelLabel = entry.models.join(', ') || '未命名'
+        const modelLabel = entry.models.join(', ') || t('admin.channels.form.unnamed')
         appStore.showError(`${platformLabel} - ${modelLabel}: ${intervalErr}`)
         activeTab.value = section.platform
         return

frontend/src/views/admin/SettingsView.vue

@@ -2804,7 +2804,7 @@ import type {
   WebSearchProviderConfig,
   WebSearchTestResult,
 } from '@/api/admin/settings'
-import type { AdminGroup, Proxy } from '@/types'
+import type { AdminGroup, Proxy, NotifyEmailEntry } from '@/types'
 import type { ProviderInstance } from '@/types/payment'
 import AppLayout from '@/components/layout/AppLayout.vue'
 import Icon from '@/components/icons/Icon.vue'
@@ -3028,7 +3028,7 @@ const form = reactive<SettingsForm>({
   balance_low_notify_enabled: false,
   balance_low_notify_threshold: 0,
   account_quota_notify_enabled: false,
-  account_quota_notify_emails: [] as { email: string; disabled: boolean; verified: boolean }[]
+  account_quota_notify_emails: [] as NotifyEmailEntry[]
 })
 
 // Proxies for web search emulation ProxySelector

frontend/src/views/user/UsageView.vue

@@ -192,7 +192,7 @@
           <template #cell-billing_mode="{ row }">
             <span class="inline-flex items-center rounded px-1.5 py-0.5 text-xs font-medium"
                   :class="getBillingModeBadgeClass(row.billing_mode)">
-              {{ getBillingModeLabel(row.billing_mode) }}
+              {{ getBillingModeLabel(row.billing_mode, t) }}
             </span>
           </template>
 
@@ -524,6 +524,7 @@ import { formatCacheTokens, formatMultiplier } from '@/utils/formatters'
 import { formatTokenPricePerMillion } from '@/utils/usagePricing'
 import { getUsageServiceTierLabel } from '@/utils/usageServiceTier'
 import { resolveUsageRequestType } from '@/utils/usageRequestType'
+import { getBillingModeLabel, getBillingModeBadgeClass } from '@/utils/billingMode'
 
 const { t } = useI18n()
 const appStore = useAppStore()
@@ -644,17 +645,6 @@ const getRequestTypeBadgeClass = (log: UsageLog): string => {
   return 'bg-amber-100 text-amber-800 dark:bg-amber-900 dark:text-amber-200'
 }
 
-const getBillingModeLabel = (mode: string | null | undefined): string => {
-  if (mode === 'per_request') return t('admin.usage.billingModePerRequest')
-  if (mode === 'image') return t('admin.usage.billingModeImage')
-  return t('admin.usage.billingModeToken')
-}
-
-const getBillingModeBadgeClass = (mode: string | null | undefined): string => {
-  if (mode === 'per_request') return 'bg-blue-100 text-blue-800 dark:bg-blue-900/30 dark:text-blue-200'
-  if (mode === 'image') return 'bg-green-100 text-green-800 dark:bg-green-900/30 dark:text-green-200'
-  return 'bg-gray-100 text-gray-800 dark:bg-gray-700 dark:text-gray-300'
-}
 
 const getRequestTypeExportText = (log: UsageLog): string => {
   const requestType = resolveUsageRequestType(log)
@@ -866,7 +856,7 @@ const exportToCSV = async () => {
         formatReasoningEffort(log.reasoning_effort),
         log.inbound_endpoint || '',
         getRequestTypeExportText(log),
-        getBillingModeLabel(log.billing_mode),
+        getBillingModeLabel(log.billing_mode, t),
         log.input_tokens,
         log.output_tokens,
         log.cache_read_tokens,