fix(channel): 全平台渠道映射覆盖 + 公共函数抽取 + 死代码清理

- 4个缺失handler入口添加渠道映射+限制检查(ChatCompletions/Responses/Gemini)
- 模型限制错误信息优化，区分"模型不可用"和"无账号"
- OpenAI RecordUsage RequestedModel 改用 OriginalModel
- ResolveChannelMappingAndRestrict/ReplaceModelInBody 抽取到 ChannelService 消除跨service重复
- validateNoDuplicateModels 按 platform:model 去重
- 删除 Channel.ResolveMappedModel 死代码和 CalculateCostWithChannel Deprecated方法
- 移除冗余nil检查，抽取 validatePricingBillingMode 公共校验

backend/internal/service/billing_service.go

@@ -402,12 +402,6 @@ func (s *BillingService) GetModelPricingWithChannel(model string, channelPricing
 	return pricing, nil
 }
 
-// CalculateCostWithChannel 使用渠道定价计算费用
-// Deprecated: 使用 CalculateCostUnified 代替
-func (s *BillingService) CalculateCostWithChannel(model string, tokens UsageTokens, rateMultiplier float64, channelPricing *ChannelModelPricing) (*CostBreakdown, error) {
-	return s.calculateCostInternal(model, tokens, rateMultiplier, "", channelPricing)
-}
-
 // --- 统一计费入口 ---
 
 // CostInput 统一计费输入

backend/internal/service/channel.go

@@ -82,38 +82,6 @@ type PricingInterval struct {
 	UpdatedAt       time.Time
 }
 
-// ResolveMappedModel 解析渠道级模型映射，返回映射后的模型名。
-// platform 指定查找哪个平台的映射规则。
-// 支持通配符（如 "claude-*" → "claude-sonnet-4"）。
-// 如果没有匹配的映射规则，返回原始模型名。
-func (c *Channel) ResolveMappedModel(platform, requestedModel string) string {
-	if len(c.ModelMapping) == 0 {
-		return requestedModel
-	}
-	platformMapping, ok := c.ModelMapping[platform]
-	if !ok || len(platformMapping) == 0 {
-		return requestedModel
-	}
-	lower := strings.ToLower(requestedModel)
-	// 精确匹配优先
-	for src, dst := range platformMapping {
-		if strings.ToLower(src) == lower {
-			return dst
-		}
-	}
-	// 通配符匹配
-	for src, dst := range platformMapping {
-		srcLower := strings.ToLower(src)
-		if strings.HasSuffix(srcLower, "*") {
-			prefix := strings.TrimSuffix(srcLower, "*")
-			if strings.HasPrefix(lower, prefix) {
-				return dst
-			}
-		}
-	}
-	return requestedModel
-}
-
 // IsActive 判断渠道是否启用
 func (c *Channel) IsActive() bool {
 	return c.Status == StatusActive

backend/internal/service/channel_service.go

@@ -11,6 +11,8 @@ import (
 
 	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
 	"golang.org/x/sync/singleflight"
 )
 
@@ -379,6 +381,34 @@ func (s *ChannelService) IsModelRestricted(ctx context.Context, groupID int64, m
 	return true
 }
 
+// ResolveChannelMappingAndRestrict 解析渠道映射并检查模型限制（组合方法）。
+// 返回映射结果和是否被限制。groupID 为 nil 时跳过。
+func (s *ChannelService) ResolveChannelMappingAndRestrict(ctx context.Context, groupID *int64, model string) (ChannelMappingResult, bool) {
+	var mapping ChannelMappingResult
+	mapping.MappedModel = model
+	if groupID == nil {
+		return mapping, false
+	}
+	mapping = s.ResolveChannelMapping(ctx, *groupID, model)
+	restricted := s.IsModelRestricted(ctx, *groupID, mapping.MappedModel)
+	return mapping, restricted
+}
+
+// ReplaceModelInBody 替换请求体 JSON 中的 model 字段。
+func ReplaceModelInBody(body []byte, newModel string) []byte {
+	if len(body) == 0 {
+		return body
+	}
+	if current := gjson.GetBytes(body, "model"); current.Exists() && current.String() == newModel {
+		return body
+	}
+	newBody, err := sjson.SetBytes(body, "model", newModel)
+	if err != nil {
+		return body
+	}
+	return newBody
+}
+
 // --- CRUD ---
 
 // Create 创建渠道
@@ -539,16 +569,16 @@ func (s *ChannelService) List(ctx context.Context, params pagination.PaginationP
 	return s.repo.List(ctx, params, status, search)
 }
 
-// validateNoDuplicateModels 检查定价列表中是否有重复模型
+// validateNoDuplicateModels 检查定价列表中是否有重复模型（同一平台下不允许重复）
 func validateNoDuplicateModels(pricingList []ChannelModelPricing) error {
 	seen := make(map[string]bool)
 	for _, p := range pricingList {
 		for _, model := range p.Models {
-			lower := strings.ToLower(model)
-			if seen[lower] {
-				return infraerrors.BadRequest("DUPLICATE_MODEL", fmt.Sprintf("model '%s' appears in multiple pricing entries", model))
+			key := p.Platform + ":" + strings.ToLower(model)
+			if seen[key] {
+				return infraerrors.BadRequest("DUPLICATE_MODEL", fmt.Sprintf("model '%s' appears in multiple pricing entries for platform '%s'", model, p.Platform))
 			}
-			seen[lower] = true
+			seen[key] = true
 		}
 	}
 	return nil

backend/internal/service/gateway_service.go

@@ -872,17 +872,7 @@ type anthropicMetadataPayload struct {
 // replaceModelInBody 替换请求体中的model字段
 // 优先使用定点修改，尽量保持客户端原始字段顺序。
 func (s *GatewayService) replaceModelInBody(body []byte, newModel string) []byte {
-	if len(body) == 0 {
-		return body
-	}
-	if current := gjson.GetBytes(body, "model"); current.Exists() && current.String() == newModel {
-		return body
-	}
-	newBody, err := sjson.SetBytes(body, "model", newModel)
-	if err != nil {
-		return body
-	}
-	return newBody
+	return ReplaceModelInBody(body, newModel)
 }
 
 type claudeOAuthNormalizeOptions struct {
@@ -7794,11 +7784,8 @@ func (s *GatewayService) RecordUsage(ctx context.Context, input *RecordUsageInpu
 		}
 		var err error
 		if s.resolver != nil && apiKey.Group != nil {
-			var groupID *int64
-			if apiKey.Group != nil {
-				gid := apiKey.Group.ID
-				groupID = &gid
-			}
+			gid := apiKey.Group.ID
+			groupID := &gid
 			cost, err = s.billingService.CalculateCostUnified(CostInput{
 				Ctx:            ctx,
 				Model:          billingModel,
@@ -8184,7 +8171,7 @@ func (s *GatewayService) ResolveChannelMapping(ctx context.Context, groupID int6
 
 // ReplaceModelInBody 替换请求体中的模型名（导出供 handler 使用）
 func (s *GatewayService) ReplaceModelInBody(body []byte, newModel string) []byte {
-	return s.replaceModelInBody(body, newModel)
+	return ReplaceModelInBody(body, newModel)
 }
 
 // IsModelRestricted 检查模型是否被渠道限制
@@ -8198,14 +8185,10 @@ func (s *GatewayService) IsModelRestricted(ctx context.Context, groupID int64, m
 // ResolveChannelMappingAndRestrict 解析渠道映射并检查模型限制。
 // 返回映射结果和是否被限制。
 func (s *GatewayService) ResolveChannelMappingAndRestrict(ctx context.Context, groupID *int64, model string) (ChannelMappingResult, bool) {
-	var mapping ChannelMappingResult
-	mapping.MappedModel = model
-	if groupID == nil {
-		return mapping, false
+	if s.channelService == nil {
+		return ChannelMappingResult{MappedModel: model}, false
 	}
-	mapping = s.ResolveChannelMapping(ctx, *groupID, model)
-	restricted := s.IsModelRestricted(ctx, *groupID, mapping.MappedModel)
-	return mapping, restricted
+	return s.channelService.ResolveChannelMappingAndRestrict(ctx, groupID, model)
 }
 
 // ForwardCountTokens 转发 count_tokens 请求到上游 API

backend/internal/service/openai_gateway_service.go

@@ -416,29 +416,15 @@ func (s *OpenAIGatewayService) IsModelRestricted(ctx context.Context, groupID in
 // ResolveChannelMappingAndRestrict 解析渠道映射并检查模型限制。
 // 返回映射结果和是否被限制。
 func (s *OpenAIGatewayService) ResolveChannelMappingAndRestrict(ctx context.Context, groupID *int64, model string) (ChannelMappingResult, bool) {
-	var mapping ChannelMappingResult
-	mapping.MappedModel = model
-	if groupID == nil {
-		return mapping, false
+	if s.channelService == nil {
+		return ChannelMappingResult{MappedModel: model}, false
 	}
-	mapping = s.ResolveChannelMapping(ctx, *groupID, model)
-	restricted := s.IsModelRestricted(ctx, *groupID, mapping.MappedModel)
-	return mapping, restricted
+	return s.channelService.ResolveChannelMappingAndRestrict(ctx, groupID, model)
 }
 
 // ReplaceModelInBody 替换请求体中的 JSON model 字段（通用 gjson/sjson 实现）。
 func (s *OpenAIGatewayService) ReplaceModelInBody(body []byte, newModel string) []byte {
-	if len(body) == 0 {
-		return body
-	}
-	if current := gjson.GetBytes(body, "model"); current.Exists() && current.String() == newModel {
-		return body
-	}
-	newBody, err := sjson.SetBytes(body, "model", newModel)
-	if err != nil {
-		return body
-	}
-	return newBody
+	return ReplaceModelInBody(body, newModel)
 }
 
 func (s *OpenAIGatewayService) getCodexSnapshotThrottle() *accountWriteThrottle {
@@ -4249,13 +4235,20 @@ func (s *OpenAIGatewayService) RecordUsage(ctx context.Context, input *OpenAIRec
 	durationMs := int(result.Duration.Milliseconds())
 	accountRateMultiplier := account.BillingRateMultiplier()
 	requestID := resolveUsageBillingRequestID(ctx, result.RequestID)
+
+	// 确定 RequestedModel（渠道映射前的原始模型）
+	requestedModel := result.Model
+	if input.OriginalModel != "" {
+		requestedModel = input.OriginalModel
+	}
+
 	usageLog := &UsageLog{
 		UserID:                user.ID,
 		APIKeyID:              apiKey.ID,
 		AccountID:             account.ID,
 		RequestID:             requestID,
 		Model:                 result.Model,
-		RequestedModel:        result.Model,
+		RequestedModel:        requestedModel,
 		UpstreamModel:         optionalNonEqualStringPtr(result.UpstreamModel, result.Model),
 		ServiceTier:           result.ServiceTier,
 		ReasoningEffort:       result.ReasoningEffort,