清理冗余的梯度返佣(TierCommission)配置

- 移除 Model 层：删除 ShopSeriesCommissionTier 模型及相关字段
- 更新 DTO：删除 TierCommissionConfig、TierEntry 类型及相关请求/响应字段
- 删除 Store 层：移除 ShopSeriesCommissionTierStore 及相关查询逻辑
- 简化 Service 层：删除梯度返佣处理逻辑，统计查询移除 tier_bonus 字段
- 数据库迁移：创建 000034_remove_tier_commission 移除相关表和字段
- 更新测试：移除梯度返佣相关测试用例，更新集成测试
- OpenAPI 文档：删除梯度返佣相关 schema 和枚举值
- 归档变更：归档 remove-tier-commission-redundancy 到 archive/2026-01-30-
- 同步规范：更新 4 个主 specs，标记废弃功能并添加迁移指引

原因：梯度返佣功能与一次性梯度佣金功能重复，且从未实现实际计算逻辑
迁移：使用一次性佣金的梯度模式 (OneTimeCommissionConfig.type = "tiered") 替代

internal/service/shop_series_allocation/service.go

@@ -16,7 +16,6 @@ import (
 
 type Service struct {
 	allocationStore            *postgres.ShopSeriesAllocationStore
-	tierStore                  *postgres.ShopSeriesCommissionTierStore
 	configStore                *postgres.ShopSeriesAllocationConfigStore
 	oneTimeCommissionTierStore *postgres.ShopSeriesOneTimeCommissionTierStore
 	shopStore                  *postgres.ShopStore
@@ -26,7 +25,6 @@ type Service struct {
 
 func New(
 	allocationStore *postgres.ShopSeriesAllocationStore,
-	tierStore *postgres.ShopSeriesCommissionTierStore,
 	configStore *postgres.ShopSeriesAllocationConfigStore,
 	oneTimeCommissionTierStore *postgres.ShopSeriesOneTimeCommissionTierStore,
 	shopStore *postgres.ShopStore,
@@ -35,7 +33,6 @@ func New(
 ) *Service {
 	return &Service{
 		allocationStore:            allocationStore,
-		tierStore:                  tierStore,
 		configStore:                configStore,
 		oneTimeCommissionTierStore: oneTimeCommissionTierStore,
 		shopStore:                  shopStore,
@@ -106,13 +103,12 @@ func (s *Service) Create(ctx context.Context, req *dto.CreateShopSeriesAllocatio
 	}
 
 	allocation := &model.ShopSeriesAllocation{
-		ShopID:               req.ShopID,
-		SeriesID:             req.SeriesID,
-		AllocatorShopID:      allocatorShopID,
-		BaseCommissionMode:   req.BaseCommission.Mode,
-		BaseCommissionValue:  req.BaseCommission.Value,
-		EnableTierCommission: req.EnableTierCommission,
-		Status:               constants.StatusEnabled,
+		ShopID:              req.ShopID,
+		SeriesID:            req.SeriesID,
+		AllocatorShopID:     allocatorShopID,
+		BaseCommissionMode:  req.BaseCommission.Mode,
+		BaseCommissionValue: req.BaseCommission.Value,
+		Status:              constants.StatusEnabled,
 	}
 
 	// 处理一次性佣金配置
@@ -192,12 +188,6 @@ func (s *Service) Update(ctx context.Context, id uint, req *dto.UpdateShopSeries
 		allocation.BaseCommissionMode = req.BaseCommission.Mode
 		allocation.BaseCommissionValue = req.BaseCommission.Value
 	}
-	if req.EnableTierCommission != nil {
-		if allocation.EnableTierCommission != *req.EnableTierCommission {
-			configChanged = true
-		}
-		allocation.EnableTierCommission = *req.EnableTierCommission
-	}
 
 	enableOneTimeCommission := allocation.EnableOneTimeCommission
 	if req.EnableOneTimeCommission != nil {
@@ -409,7 +399,6 @@ func (s *Service) buildResponse(ctx context.Context, a *model.ShopSeriesAllocati
 			Mode:  a.BaseCommissionMode,
 			Value: a.BaseCommissionValue,
 		},
-		EnableTierCommission:    a.EnableTierCommission,
 		EnableOneTimeCommission: a.EnableOneTimeCommission,
 		Status:                  a.Status,
 		CreatedAt:               a.CreatedAt.Format(time.RFC3339),
@@ -458,12 +447,11 @@ func (s *Service) createNewConfigVersion(ctx context.Context, allocation *model.
 	}
 
 	newConfig := &model.ShopSeriesAllocationConfig{
-		AllocationID:         allocation.ID,
-		Version:              newVersion,
-		BaseCommissionMode:   allocation.BaseCommissionMode,
-		BaseCommissionValue:  allocation.BaseCommissionValue,
-		EnableTierCommission: allocation.EnableTierCommission,
-		EffectiveFrom:        now,
+		AllocationID:        allocation.ID,
+		Version:             newVersion,
+		BaseCommissionMode:  allocation.BaseCommissionMode,
+		BaseCommissionValue: allocation.BaseCommissionValue,
+		EffectiveFrom:       now,
 	}
 
 	if err := s.configStore.Create(ctx, newConfig); err != nil {