feat: 商品追踪页面 + 出库提交库存校验

后端：
- feat(backend): 重命名 Batches→Products 接口，新增库存状态(在售/已卖出)和买家信息
- feat(backend): 出库单创建/提交时校验仓库库存，不足则返回明确错误信息
- fix(backend): 出库创建 status 判断逻辑修复（空值默认 draft）

前端：
- feat(client): 批次追踪改为商品追踪，新增状态列(在售/已卖出)和买家/时间列
- fix(client): 无批次号时显示"无批次"而非空
- refactor(client): BatchRecord → ProductTrackingRecord，repository 接口更新

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/handler/inventory.go

@@ -1,6 +1,7 @@
 package handler
 
 import (
+	"fmt"
 	"net/http"
 	"strconv"
 
@@ -69,13 +70,21 @@ func (h *InventoryHandler) Logs(c *gin.Context) {
 	c.JSON(http.StatusOK, gin.H{"data": logs, "total": total, "page": page, "page_size": pageSize})
 }
 
-// Batches GET /api/v1/inventory/batches — 批次追踪：已审核入库单的明细行
-func (h *InventoryHandler) Batches(c *gin.Context) {
+// productTrackingItem is the response shape for GET /api/v1/inventory/products
+type productTrackingItem struct {
+	model.StockInItem
+	CurrentQty float64 `json:"current_qty"`
+	Status     string  `json:"status"` // in_stock | sold_out
+	BuyerName  string  `json:"buyer_name,omitempty"`
+	SoldAt     string  `json:"sold_at,omitempty"`
+}
+
+// Products GET /api/v1/inventory/products — 商品追踪：已审核入库单的明细行，附库存状态和买家
+func (h *InventoryHandler) Products(c *gin.Context) {
 	shopID := middleware.GetShopID(c)
 	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
 	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
 
-	// 查询已审核的入库单明细，关联商品和仓库信息
 	query := h.db.Model(&model.StockInItem{}).
 		Joins("JOIN stock_in_orders ON stock_in_orders.id = stock_in_items.order_id").
 		Where("stock_in_orders.shop_id = ? AND stock_in_orders.status = 'approved'", shopID)
@@ -98,10 +107,76 @@ func (h *InventoryHandler) Batches(c *gin.Context) {
 		}).
 		Select("stock_in_items.*").
 		Order("stock_in_orders.order_date DESC, stock_in_items.id DESC").
-		Offset((page - 1) * pageSize).Limit(pageSize).
+		Offset((page-1)*pageSize).Limit(pageSize).
 		Find(&items)
 
-	c.JSON(http.StatusOK, gin.H{"data": items, "total": total, "page": page, "page_size": pageSize})
+	// 一次查出所有库存，构建 product+warehouse → qty 的 map
+	var inventories []model.Inventory
+	h.db.Where("shop_id = ?", shopID).Find(&inventories)
+	invMap := make(map[string]float64, len(inventories))
+	for _, inv := range inventories {
+		key := fmt.Sprintf("%d:%d", inv.ProductID, inv.WarehouseID)
+		invMap[key] = inv.Quantity
+	}
+
+	// 查询每个 product+warehouse 最新的出库买家信息
+	type soldRow struct {
+		ProductID   uint64 `gorm:"column:product_id"`
+		WarehouseID uint64 `gorm:"column:warehouse_id"`
+		BuyerName   string `gorm:"column:buyer_name"`
+		SoldAt      string `gorm:"column:sold_at"`
+	}
+	var soldRows []soldRow
+	h.db.Raw(`
+		SELECT sooi.product_id, soo.warehouse_id,
+		       COALESCE(p.name, '') AS buyer_name,
+		       CAST(MAX(soo.order_date) AS CHAR) AS sold_at
+		FROM stock_out_orders soo
+		JOIN stock_out_items sooi ON sooi.order_id = soo.id
+		LEFT JOIN partners p ON p.id = soo.partner_id AND p.shop_id = ?
+		WHERE soo.shop_id = ? AND soo.status = 'approved'
+		GROUP BY sooi.product_id, soo.warehouse_id
+	`, shopID, shopID).Scan(&soldRows)
+	soldMap := make(map[string]soldRow, len(soldRows))
+	for _, r := range soldRows {
+		key := fmt.Sprintf("%d:%d", r.ProductID, r.WarehouseID)
+		soldMap[key] = r
+	}
+
+	result := make([]productTrackingItem, 0, len(items))
+	for _, item := range items {
+		var warehouseID uint64
+		if item.Order != nil {
+			warehouseID = item.Order.WarehouseID
+		}
+		key := fmt.Sprintf("%d:%d", item.ProductID, warehouseID)
+		currentQty := invMap[key]
+
+		status := "in_stock"
+		buyerName := ""
+		soldAt := ""
+		if currentQty <= 0 {
+			status = "sold_out"
+			if si, ok := soldMap[key]; ok {
+				buyerName = si.BuyerName
+				if len(si.SoldAt) > 10 {
+					soldAt = si.SoldAt[:10]
+				} else {
+					soldAt = si.SoldAt
+				}
+			}
+		}
+
+		result = append(result, productTrackingItem{
+			StockInItem: item,
+			CurrentQty:  currentQty,
+			Status:      status,
+			BuyerName:   buyerName,
+			SoldAt:      soldAt,
+		})
+	}
+
+	c.JSON(http.StatusOK, gin.H{"data": result, "total": total, "page": page, "page_size": pageSize})
 }
 
 // CreateCheck POST /api/v1/inventory/checks