fix: prevent channel pricing overrides from mutating shared fallback pricing

backend/internal/service/billing_service.go

@@ -771,6 +771,9 @@ func (s *BillingService) GetModelPricingWithChannel(model string, channelPricing
 	if channelPricing == nil {
 		return pricing, nil
 	}
+	// 防止修改 fallbackPrices 中的共享指针
+	cloned := *pricing
+	pricing = &cloned
 	if channelPricing.InputPrice != nil {
 		pricing.InputPricePerToken = *channelPricing.InputPrice
 		pricing.InputPricePerTokenPriority = *channelPricing.InputPrice

backend/internal/service/model_pricing_resolver.go

@@ -150,6 +150,10 @@ func (r *ModelPricingResolver) applyTokenOverrides(chPricing *ChannelModelPricin
 		// 区间不匹配时回退到 BasePricing，也需要覆盖图片价格
 		if resolved.BasePricing == nil {
 			resolved.BasePricing = &ModelPricing{}
+		} else {
+			// 防止修改 fallbackPrices 中的共享指针
+			cloned := *resolved.BasePricing
+			resolved.BasePricing = &cloned
 		}
 		if chPricing.ImageOutputPrice != nil {
 			resolved.BasePricing.ImageOutputPricePerToken = *chPricing.ImageOutputPrice
@@ -163,6 +167,10 @@ func (r *ModelPricingResolver) applyTokenOverrides(chPricing *ChannelModelPricin
 	// 否则用 flat 字段覆盖 BasePricing
 	if resolved.BasePricing == nil {
 		resolved.BasePricing = &ModelPricing{}
+	} else {
+		// 防止修改 fallbackPrices 中的共享指针
+		cloned := *resolved.BasePricing
+		resolved.BasePricing = &cloned
 	}
 
 	if chPricing.InputPrice != nil {