fix(backend): 架构质量改进批次二 (#32-37)

- #32 License 激活迁移到 license_devices 表：Activate/Verify/Deactivate 全部改用
  license_devices，新增 max_devices 校验和 GET /license/devices 端点；
  Activate 现在校验 shop_id 防跨租户激活
- #33 checkInventory 从 StockOutHandler 移到 StockService.CheckInventoryAvailability
- #34 新增 util/response.go 统一错误响应工具（RespondError/RespondSuccess/RespondCreated）
- #35 生产模式 CORS Origin='*' 启动时 Fatal
- #36 生产模式 License 私钥未配置启动时 Fatal
- #37 新增 util/page.go ValidatePageSize，应用到 partner/product/stock_in/stock_out handler

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

backend/internal/handler/stock_out.go

@@ -1,7 +1,6 @@
 package handler
 
 import (
-	"fmt"
 	"net/http"
 	"strconv"
 
@@ -11,6 +10,7 @@ import (
 	"github.com/wangjia/jiu/backend/internal/middleware"
 	"github.com/wangjia/jiu/backend/internal/model"
 	"github.com/wangjia/jiu/backend/internal/service"
+	"github.com/wangjia/jiu/backend/internal/util"
 )
 
 type StockOutHandler struct {
@@ -27,6 +27,7 @@ func (h *StockOutHandler) List(c *gin.Context) {
 	shopID := middleware.GetShopID(c)
 	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
 	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
+	pageSize = util.ValidatePageSize(pageSize, 20, 200)
 
 	query := h.db.Model(&model.StockOutOrder{}).
 		Where("shop_id = ? AND deleted_at IS NULL", shopID)
@@ -65,51 +66,6 @@ func (h *StockOutHandler) Get(c *gin.Context) {
 	c.JSON(http.StatusOK, gin.H{"data": order})
 }
 
-// checkInventory validates that warehouse has enough stock for each item (SUM aggregate).
-// warehouseID is the order's warehouse; items are the stock-out line items.
-func (h *StockOutHandler) checkInventory(shopID, warehouseID uint64, items []model.StockOutItem) error {
-	if len(items) == 0 {
-		return nil
-	}
-
-	// Collect product IDs
-	productIDs := make([]uint64, 0, len(items))
-	for _, item := range items {
-		productIDs = append(productIDs, item.ProductID)
-	}
-
-	type inventorySum struct {
-		ProductID uint64
-		Total     float64
-	}
-	var sums []inventorySum
-	h.db.Model(&model.Inventory{}).
-		Select("product_id, COALESCE(SUM(quantity), 0) AS total").
-		Where("shop_id = ? AND warehouse_id = ? AND product_id IN ? AND deleted_at IS NULL",
-			shopID, warehouseID, productIDs).
-		Group("product_id").Scan(&sums)
-
-	// Build map for quick lookup
-	sumMap := make(map[uint64]float64, len(sums))
-	for _, s := range sums {
-		sumMap[s.ProductID] = s.Total
-	}
-
-	for _, item := range items {
-		have := sumMap[item.ProductID]
-		if have < item.Quantity {
-			// Get product name for a clearer error message
-			var p model.Product
-			h.db.Where("id = ?", item.ProductID).First(&p)
-			name := p.Name
-			if name == "" {
-				name = fmt.Sprintf("商品ID %d", item.ProductID)
-			}
-			return fmt.Errorf("库存不足：%s 当前库存 %.0f，需要 %.0f", name, have, item.Quantity)
-		}
-	}
-	return nil
-}
 
 // Create POST /api/v1/stock-out/orders
 func (h *StockOutHandler) Create(c *gin.Context) {
@@ -127,7 +83,7 @@ func (h *StockOutHandler) Create(c *gin.Context) {
 
 	// 状态只允许 draft 或 pending；直接提交审核时校验库存
 	if req.Status == "pending" {
-		if err := h.checkInventory(shopID, req.WarehouseID, req.Items); err != nil {
+		if err := h.stockSvc.CheckInventoryAvailability(shopID, req.WarehouseID, req.Items); err != nil {
 			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
 			return
 		}
@@ -235,7 +191,7 @@ func (h *StockOutHandler) Submit(c *gin.Context) {
 		c.JSON(http.StatusBadRequest, gin.H{"error": "order not found or not in draft status"})
 		return
 	}
-	if err := h.checkInventory(shopID, order.WarehouseID, order.Items); err != nil {
+	if err := h.stockSvc.CheckInventoryAvailability(shopID, order.WarehouseID, order.Items); err != nil {
 		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
 		return
 	}