feat(channel): 渠道管理全链路集成 — 模型映射、定价、限制、用量统计

- 渠道模型映射：支持精确匹配和通配符映射，按平台隔离
- 渠道模型定价：支持 token/按次/图片三种计费模式，区间分层定价
- 模型限制：渠道可限制仅允许定价列表中的模型
- 计费模型来源：支持 requested/upstream 两种计费模型选择
- 用量统计：usage_logs 新增 channel_id/model_mapping_chain/billing_tier/billing_mode 字段
- Dashboard 支持 model_source 维度（requested/upstream/mapping）查看模型统计
- 全部 gateway handler 统一接入 ResolveChannelMappingAndRestrict
- 修复测试：同步 SoraGenerationRepository 接口、SQL INSERT 参数、scan 字段

backend/internal/repository/usage_log_repo.go

@@ -3144,6 +3144,30 @@ func (r *usageLogRepository) GetUserBreakdownStats(ctx context.Context, startTim
 		query += fmt.Sprintf(" AND %s = $%d", col, len(args)+1)
 		args = append(args, dim.Endpoint)
 	}
+	if dim.UserID > 0 {
+		query += fmt.Sprintf(" AND ul.user_id = $%d", len(args)+1)
+		args = append(args, dim.UserID)
+	}
+	if dim.APIKeyID > 0 {
+		query += fmt.Sprintf(" AND ul.api_key_id = $%d", len(args)+1)
+		args = append(args, dim.APIKeyID)
+	}
+	if dim.AccountID > 0 {
+		query += fmt.Sprintf(" AND ul.account_id = $%d", len(args)+1)
+		args = append(args, dim.AccountID)
+	}
+	if dim.RequestType != nil {
+		query += fmt.Sprintf(" AND ul.request_type = $%d", len(args)+1)
+		args = append(args, *dim.RequestType)
+	}
+	if dim.Stream != nil {
+		query += fmt.Sprintf(" AND ul.stream = $%d", len(args)+1)
+		args = append(args, *dim.Stream)
+	}
+	if dim.BillingType != nil {
+		query += fmt.Sprintf(" AND ul.billing_type = $%d", len(args)+1)
+		args = append(args, *dim.BillingType)
+	}
 
 	query += " GROUP BY ul.user_id, u.email ORDER BY actual_cost DESC"
 	if limit > 0 {