fix(exports): 优化导出接口的行数估算逻辑

- 修改估算行数的回退逻辑，使用精确 COUNT 替代原先的快速估算
- 添加日志记录精确统计阶段的相关信息，便于跟踪统计过程
- 修正导出接口的估算准确性，提升导出性能和稳定性

fix(metadata): 隐藏 marketingMetadataTables 中键“绑定类型”字段

- 将绑定类型字段的 Hidden 属性由 false 改为 true
- 避免绑定类型字段在某些场景下被展示
- 保持批次相关字段显示的合理性和安全性

server/internal/api/exports.go

@@ -305,7 +305,7 @@ func (a *ExportsAPI) create(w http.ResponseWriter, r *http.Request) {
 		fail(w, r, http.StatusBadRequest, fmt.Sprintf("EXPLAIN 未通过：评分=%d，请优化索引或缩小查询范围", score))
 		return
 	}
-	// 估算行数（优先使用分块统计，失败或结果为 0 时回退到单次 COUNT）
+	// 估算行数（优先使用分块统计，失败或结果为 0 时回退到精确 COUNT）
 	var estimate int64
 	estimate = rrepo.EstimateFastChunked(dataDB, ds, main, p.Filters)
 	if estimate <= 0 {
@@ -314,8 +314,20 @@ func (a *ExportsAPI) create(w http.ResponseWriter, r *http.Request) {
 			"datasource": ds,
 			"main_table": main,
 			"filters":    p.Filters,
+			"stage":      "fast_chunked",
+			"estimate":   estimate,
+		})
+		// 使用完整导出 SQL 做一次精确统计，避免分表/索引等原因导致估算为 0
+		estimate = exporter.CountRows(dataDB, q, args)
+		logging.JSON("INFO", map[string]interface{}{
+			"event":      "estimate_exact_count",
+			"datasource": ds,
+			"main_table": main,
+			"filters":    p.Filters,
+			"sql":        q,
+			"args":       args,
+			"estimate":   estimate,
 		})
-		estimate = rrepo.EstimateFast(dataDB, ds, main, p.Filters)
 	}
 	hdrs := make([]string, len(filtered))
 	for i, tf := range filtered {

server/internal/api/metadata.go

@@ -95,7 +95,7 @@ func marketingMetadataTables() []tableInfo {
 				{Key: "key_batch.plan_id", Field: "plan_id", Label: "计划编号", Hidden: true},
 				{Key: "key_batch.style", Field: "style", Label: "KEY样式", Hidden: false},
 				{Key: "key_batch.batch_name", Field: "batch_name", Label: "KEY批次名称", Hidden: false},
-				{Key: "key_batch.bind_object", Field: "bind_object", Label: "绑定类型", Hidden: false},
+				{Key: "key_batch.bind_object", Field: "bind_object", Label: "绑定类型", Hidden: true},
 				{Key: "key_batch.quantity", Field: "quantity", Label: "发放KEY数量", Hidden: true},
 				{Key: "key_batch.stock", Field: "stock", Label: "剩余库存信息", Hidden: true},
 				{Key: "key_batch.allow_repetition", Field: "allow_repetition", Label: "允许商品重复选择：1允许，0不允许", Hidden: true},