refactor(channels): centralize BillingModelSource normalization and exhaustive enum maps

- service: add normalizeBillingModelSource helper, apply in Create/GetByID/Update/List/ListAvailable outputs
- handler: drop channelToResponse fallback now that service owns the default; add passthrough test
- frontend: replace ternary status/billing-source lookups with Record<Enum, ...> maps so new union members fail the build
- chip/table: drop local type aliases, reuse UserSupportedModel/UserPricingInterval directly
- tests: assert short-circuit on ListAll error, wrap-prefix preservation, and Name-based default lookup

backend/internal/service/channel_available.go

@@ -32,6 +32,9 @@ type AvailableChannel struct {
 // 支持模型通过 (*Channel).SupportedModels() 计算得到（见 channel.go）。
 // 关联分组信息通过 groupRepo.ListActive 查询后按 ID 映射；渠道 GroupIDs 中未在活跃列表中
 // 的分组（已停用或删除）会被忽略。
+//
+// 前置条件：s.groupRepo 必须非 nil（由 wire DI 保证）。直接 nil-deref 用于 fail-fast，
+// 避免静默掩盖注入缺失。
 func (s *ChannelService) ListAvailable(ctx context.Context) ([]AvailableChannel, error) {
 	channels, err := s.repo.ListAll(ctx)
 	if err != nil {
@@ -61,19 +64,16 @@ func (s *ChannelService) ListAvailable(ctx context.Context) ([]AvailableChannel,
 				groups = append(groups, ref)
 			}
 		}
-		sort.Slice(groups, func(i, j int) bool { return groups[i].Name < groups[j].Name })
+		sort.SliceStable(groups, func(i, j int) bool { return groups[i].Name < groups[j].Name })
 
-		billingSource := ch.BillingModelSource
-		if billingSource == "" {
-			billingSource = BillingModelSourceChannelMapped
-		}
+		normalizeBillingModelSource(ch)
 
 		out = append(out, AvailableChannel{
 			ID:                 ch.ID,
 			Name:               ch.Name,
 			Description:        ch.Description,
 			Status:             ch.Status,
-			BillingModelSource: billingSource,
+			BillingModelSource: ch.BillingModelSource,
 			RestrictModels:     ch.RestrictModels,
 			Groups:             groups,
 			SupportedModels:    ch.SupportedModels(),

backend/internal/service/channel_available_test.go

@@ -14,12 +14,15 @@ import (
 // stubGroupRepoForAvailable 是 ListAvailable 测试用的 GroupRepository stub，
 // 仅实现 ListActive；其他方法对本测试无关，返回零值即可。
 // listActiveErr 非 nil 时，ListActive 返回该错误用于错误传播测试。
+// listActiveCalls 记录调用次数，用于断言「失败短路时不再访问 groupRepo」等行为。
 type stubGroupRepoForAvailable struct {
-	activeGroups  []Group
-	listActiveErr error
+	activeGroups    []Group
+	listActiveErr   error
+	listActiveCalls int
 }
 
 func (s *stubGroupRepoForAvailable) ListActive(ctx context.Context) ([]Group, error) {
+	s.listActiveCalls++
 	if s.listActiveErr != nil {
 		return nil, s.listActiveErr
 	}
@@ -125,15 +128,18 @@ func TestListAvailable_SortedByName(t *testing.T) {
 }
 
 func TestListAvailable_ListAllErrorPropagates(t *testing.T) {
-	// ListAll 返回错误时 ListAvailable 应直接返回包装后的错误，不再访问 groupRepo。
+	// ListAll 返回错误时 ListAvailable 应直接返回包装后的错误，且不再访问 groupRepo（短路）。
 	sentinel := errors.New("list-all-boom")
 	repo := &mockChannelRepository{
 		listAllFn: func(ctx context.Context) ([]Channel, error) { return nil, sentinel },
 	}
-	svc := NewChannelService(repo, &stubGroupRepoForAvailable{}, nil)
+	groupRepo := &stubGroupRepoForAvailable{}
+	svc := NewChannelService(repo, groupRepo, nil)
 	out, err := svc.ListAvailable(context.Background())
 	require.Nil(t, out)
 	require.ErrorIs(t, err, sentinel)
+	require.Contains(t, err.Error(), "list channels", "wrap 前缀缺失，可能 %w 被改为 %v")
+	require.Equal(t, 0, groupRepo.listActiveCalls, "ListAll 失败后不应再调用 groupRepo.ListActive")
 }
 
 func TestListAvailable_ListActiveErrorPropagates(t *testing.T) {
@@ -146,6 +152,7 @@ func TestListAvailable_ListActiveErrorPropagates(t *testing.T) {
 	out, err := svc.ListAvailable(context.Background())
 	require.Nil(t, out)
 	require.ErrorIs(t, err, sentinel)
+	require.Contains(t, err.Error(), "list active groups", "wrap 前缀缺失，可能 %w 被改为 %v")
 }
 
 func TestListAvailable_DefaultsEmptyBillingModelSource(t *testing.T) {
@@ -159,6 +166,12 @@ func TestListAvailable_DefaultsEmptyBillingModelSource(t *testing.T) {
 	out, err := svc.ListAvailable(context.Background())
 	require.NoError(t, err)
 	require.Len(t, out, 2)
-	require.Equal(t, BillingModelSourceChannelMapped, out[0].BillingModelSource)
-	require.Equal(t, BillingModelSourceUpstream, out[1].BillingModelSource)
+
+	// 按 Name 查找，避免依赖排序副作用。
+	byName := make(map[string]string, len(out))
+	for _, ch := range out {
+		byName[ch.Name] = ch.BillingModelSource
+	}
+	require.Equal(t, BillingModelSourceChannelMapped, byName["empty"])
+	require.Equal(t, BillingModelSourceUpstream, byName["explicit"])
 }

backend/internal/service/channel_service.go

@@ -686,9 +686,7 @@ func (s *ChannelService) Create(ctx context.Context, input *CreateChannelInput)
 		ApplyPricingToAccountStats: input.ApplyPricingToAccountStats,
 		AccountStatsPricingRules:   input.AccountStatsPricingRules,
 	}
-	if channel.BillingModelSource == "" {
-		channel.BillingModelSource = BillingModelSourceChannelMapped
-	}
+	normalizeBillingModelSource(channel)
 
 	if err := validateChannelConfig(channel.ModelPricing, channel.ModelMapping); err != nil {
 		return nil, err
@@ -704,12 +702,31 @@ func (s *ChannelService) Create(ctx context.Context, input *CreateChannelInput)
 	}
 
 	s.invalidateCache()
-	return s.repo.GetByID(ctx, channel.ID)
+	created, err := s.repo.GetByID(ctx, channel.ID)
+	if err != nil {
+		return nil, err
+	}
+	normalizeBillingModelSource(created)
+	return created, nil
 }
 
-// GetByID 获取渠道详情
+// GetByID 获取渠道详情。返回前统一把空 BillingModelSource 回填为 ChannelMapped，
+// 让所有 handler 无需重复处理历史空值。
 func (s *ChannelService) GetByID(ctx context.Context, id int64) (*Channel, error) {
-	return s.repo.GetByID(ctx, id)
+	ch, err := s.repo.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	normalizeBillingModelSource(ch)
+	return ch, nil
+}
+
+// normalizeBillingModelSource 若 BillingModelSource 为空则回填默认值 ChannelMapped。
+// 统一在 service 层完成，避免 handler 响应层重复兜底。
+func normalizeBillingModelSource(ch *Channel) {
+	if ch != nil && ch.BillingModelSource == "" {
+		ch.BillingModelSource = BillingModelSourceChannelMapped
+	}
 }
 
 // Update 更新渠道
@@ -741,7 +758,12 @@ func (s *ChannelService) Update(ctx context.Context, id int64, input *UpdateChan
 	s.invalidateCache()
 	s.invalidateAuthCacheForGroups(ctx, oldGroupIDs, channel.GroupIDs)
 
-	return s.repo.GetByID(ctx, id)
+	updated, err := s.repo.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	normalizeBillingModelSource(updated)
+	return updated, nil
 }
 
 // applyUpdateInput 将更新请求的字段应用到渠道实体上。
@@ -859,7 +881,14 @@ func (s *ChannelService) Delete(ctx context.Context, id int64) error {
 
 // List 获取渠道列表
 func (s *ChannelService) List(ctx context.Context, params pagination.PaginationParams, status, search string) ([]Channel, *pagination.PaginationResult, error) {
-	return s.repo.List(ctx, params, status, search)
+	channels, res, err := s.repo.List(ctx, params, status, search)
+	if err != nil {
+		return nil, nil, err
+	}
+	for i := range channels {
+		normalizeBillingModelSource(&channels[i])
+	}
+	return channels, res, nil
 }
 
 // modelEntry 表示一个模型模式条目（用于冲突检测）