fix: address audit findings - cache sync, validation, consistency

- clearCreditsExhausted: sync Redis scheduler cache after DB update
- Image billing mode UI: write to per_request_price instead of image_output_price
- OpenAI RecordUsage: use BillingModelSourceRequested constant, add s.cfg nil guard
- Fix i18n key path: admin.channels.perRequestPriceRequired → admin.channels.form.perRequestPriceRequired

backend/internal/service/antigravity_credits_overages.go

@@ -140,6 +140,10 @@ func (s *AntigravityGatewayService) clearCreditsExhausted(ctx context.Context, a
 	}); err != nil {
 		logger.LegacyPrintf("service.antigravity_gateway", "clear credits exhausted failed: account=%d err=%v", account.ID, err)
 	}
+	// 同步更新 Redis 调度快照，避免其他节点/请求延迟感知
+	if s.schedulerSnapshot != nil {
+		_ = s.schedulerSnapshot.UpdateAccountInCache(ctx, account)
+	}
 }
 
 // classifyAntigravity429 将 Antigravity 的 429 响应归类为配额耗尽、限流或未知。

backend/internal/service/openai_gateway_service.go

@@ -4182,7 +4182,10 @@ func (s *OpenAIGatewayService) RecordUsage(ctx context.Context, input *OpenAIRec
 	}
 
 	// Get rate multiplier
-	multiplier := s.cfg.Default.RateMultiplier
+	multiplier := 1.0
+	if s.cfg != nil {
+		multiplier = s.cfg.Default.RateMultiplier
+	}
 	if apiKey.GroupID != nil && apiKey.Group != nil {
 		resolver := s.userGroupRateResolver
 		if resolver == nil {
@@ -4200,7 +4203,7 @@ func (s *OpenAIGatewayService) RecordUsage(ctx context.Context, input *OpenAIRec
 	if input.BillingModelSource == BillingModelSourceChannelMapped && input.ChannelMappedModel != "" {
 		billingModel = input.ChannelMappedModel
 	}
-	if input.BillingModelSource == "requested" && input.OriginalModel != "" {
+	if input.BillingModelSource == BillingModelSourceRequested && input.OriginalModel != "" {
 		billingModel = input.OriginalModel
 	}
 	serviceTier := ""

frontend/src/components/admin/channel/PricingEntryCard.vue

@@ -191,13 +191,13 @@
 
         <!-- Image mode -->
         <div v-else-if="entry.billing_mode === 'image'">
-          <!-- Default image price -->
+          <!-- Default image price (per-request, same as per_request mode) -->
           <label class="mt-3 block text-xs font-medium text-gray-500 dark:text-gray-400">
             {{ t('admin.channels.form.defaultImagePrice', '默认图片价格（未命中层级时使用）') }}
             <span class="ml-1 font-normal text-gray-400">$</span>
           </label>
           <div class="mt-1 w-48">
-            <input :value="entry.image_output_price" @input="emitField('image_output_price', ($event.target as HTMLInputElement).value)"
+            <input :value="entry.per_request_price" @input="emitField('per_request_price', ($event.target as HTMLInputElement).value)"
               type="number" step="any" min="0" class="input text-sm" :placeholder="t('admin.channels.form.pricePlaceholder', '默认')" />
           </div>
 

frontend/src/views/admin/ChannelsView.vue

@@ -916,7 +916,7 @@ async function handleSubmit() {
       if ((entry.billing_mode === 'per_request' || entry.billing_mode === 'image') &&
           (entry.per_request_price == null || entry.per_request_price === '') &&
           (!entry.intervals || entry.intervals.length === 0)) {
-        appStore.showError(t('admin.channels.perRequestPriceRequired', '按次/图片计费模式必须设置默认价格或至少一个计费层级'))
+        appStore.showError(t('admin.channels.form.perRequestPriceRequired', '按次/图片计费模式必须设置默认价格或至少一个计费层级'))
         return
       }
     }