feat: remove shipping settings, use shipping templates for cart calculation

backend/internal/api/handlers/shipping_template.go

@@ -258,3 +258,20 @@ func CalculateShippingFee(templateID *uint, weight float64, quantity int, subtot
 
 	return template.FirstFee + additionalCount*template.AdditionalFee, nil
 }
+
+// CalculateForUser 用户端计算运费接口
+func (h *ShippingTemplateHandler) CalculateForUser(c *gin.Context) {
+	var req schemas.CalculateShippingRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	fee, err := CalculateShippingFee(req.TemplateID, req.Weight, req.Quantity, req.Subtotal, req.Province)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "计算运费失败"})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{"data": gin.H{"shipping_fee": fee}})
+}