feat: 库存 XLS 导入功能（后端接口 + 前端导入按钮）

backend/internal/handler/import.go

@@ -468,6 +468,134 @@ func (h *ImportHandler) ImportStockOut(c *gin.Context) {
 	c.JSON(http.StatusOK, gin.H{"order_no": orderNo, "items": len(items)})
 }
 
+// ImportInventory POST /api/v1/import/inventory
+// 列顺序：商品编号,商品名称,系列,规格,单位,库存数量,单价,金额,生产日期,批次,分类,所在仓库,入库日期,供应商,上次盘点,备注
+func (h *ImportHandler) ImportInventory(c *gin.Context) {
+	shopID := middleware.GetShopID(c)
+
+	rows, err := parseUploadedExcel(c)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	type result struct {
+		imported int
+		skipped  int
+		errors   []string
+	}
+	var res result
+
+	// 仓库缓存，避免重复查询
+	warehouseCache := map[string]uint64{}
+	findOrCreateWarehouse := func(name string) (uint64, error) {
+		if name == "" {
+			name = "默认仓库"
+		}
+		if id, ok := warehouseCache[name]; ok {
+			return id, nil
+		}
+		var wh model.Warehouse
+		if h.db.Where("shop_id = ? AND name = ? AND deleted_at IS NULL", shopID, name).First(&wh).Error != nil {
+			wh = model.Warehouse{
+				TenantBase: model.TenantBase{ShopID: shopID},
+				Name:       name,
+			}
+			if err := h.db.Create(&wh).Error; err != nil {
+				return 0, err
+			}
+		}
+		warehouseCache[name] = wh.ID
+		return wh.ID, nil
+	}
+
+	for i, row := range rows[1:] {
+		productName := cell(row, 1)
+		if productName == "" {
+			res.skipped++
+			continue
+		}
+		series := cell(row, 2)
+		spec := cell(row, 3)
+		unit := cell(row, 4)
+		qtyStr := cell(row, 5)
+		priceStr := cell(row, 6)
+		warehouseName := cell(row, 11)
+
+		qty, _ := strconv.ParseFloat(qtyStr, 64)
+		price, _ := strconv.ParseFloat(priceStr, 64)
+
+		// 找或创建商品
+		prod, err := findOrCreateProductFn(h.db, shopID, productName, series, spec)
+		if err != nil {
+			res.errors = append(res.errors, fmt.Sprintf("行%d: 商品创建失败: %s", i+2, err.Error()))
+			continue
+		}
+		if unit != "" && prod.Unit == "" {
+			h.db.Model(&prod).Update("unit", unit)
+		}
+		if price > 0 && prod.PurchasePrice == 0 {
+			h.db.Model(&prod).Update("purchase_price", price)
+		}
+
+		// 找或创建仓库
+		whID, err := findOrCreateWarehouse(warehouseName)
+		if err != nil {
+			res.errors = append(res.errors, fmt.Sprintf("行%d: 仓库创建失败: %s", i+2, err.Error()))
+			continue
+		}
+
+		// upsert 库存数量
+		err = h.db.Transaction(func(tx *gorm.DB) error {
+			var inv model.Inventory
+			isNew := false
+			if tx.Where("shop_id = ? AND warehouse_id = ? AND product_id = ?",
+				shopID, whID, prod.ID).First(&inv).Error != nil {
+				inv = model.Inventory{
+					ShopID:      shopID,
+					WarehouseID: whID,
+					ProductID:   prod.ID,
+				}
+				isNew = true
+			}
+			qtyBefore := inv.Quantity
+			inv.Quantity = qty
+			if isNew {
+				if err := tx.Create(&inv).Error; err != nil {
+					return err
+				}
+			} else {
+				if err := tx.Save(&inv).Error; err != nil {
+					return err
+				}
+			}
+			// 写流水
+			log := model.InventoryLog{
+				ShopID:      shopID,
+				WarehouseID: whID,
+				ProductID:   prod.ID,
+				Direction:   "in",
+				Quantity:    qty,
+				QtyBefore:   qtyBefore,
+				QtyAfter:    qty,
+				RefType:     "import",
+			}
+			return tx.Create(&log).Error
+		})
+		if err != nil {
+			res.errors = append(res.errors, fmt.Sprintf("行%d: 库存写入失败: %s", i+2, err.Error()))
+			continue
+		}
+		res.imported++
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"imported": res.imported,
+		"skipped":  res.skipped,
+		"errors":   res.errors,
+	})
+}
+
 // ── 内部辅助函数 ─────────────────────────────────────────────
 
 func parseUploadedExcel(c *gin.Context) ([][]string, error) {