优化小程序阅读页面，新增好友优惠展示逻辑，支持通过推荐人获取折扣。调整价格计算方式，确保用户在购买章节时能看到实际优惠。更新相关样式以提升用户体验。

soul-api/internal/handler/db.go

@@ -91,6 +91,19 @@ func GetPublicDBConfig(c *gin.Context) {
 			}
 		}
 	}
+	// 好友优惠（用于 read 页展示优惠价）
+	var refRow model.SystemConfig
+	if err := db.Where("config_key = ?", "referral_config").First(&refRow).Error; err == nil {
+		var refVal map[string]interface{}
+		if err := json.Unmarshal(refRow.ConfigValue, &refVal); err == nil {
+			if v, ok := refVal["userDiscount"].(float64); ok {
+				out["userDiscount"] = v
+			}
+		}
+	}
+	if _, has := out["userDiscount"]; !has {
+		out["userDiscount"] = float64(5)
+	}
 	c.JSON(http.StatusOK, out)
 }
 
@@ -223,8 +236,9 @@ func AdminReferralSettingsGet(c *gin.Context) {
 	defaultConfig := gin.H{
 		"distributorShare":   float64(90),
 		"minWithdrawAmount":  float64(10),
-		"bindingDays":       float64(30),
-		"userDiscount":      float64(5),
+		"bindingDays":        float64(30),
+		"userDiscount":       float64(5),
+		"withdrawFee":        float64(5),
 		"enableAutoWithdraw": false,
 	}
 	var row model.SystemConfig
@@ -247,6 +261,7 @@ func AdminReferralSettingsPost(c *gin.Context) {
 		MinWithdrawAmount  float64 `json:"minWithdrawAmount"`
 		BindingDays        float64 `json:"bindingDays"`
 		UserDiscount       float64 `json:"userDiscount"`
+		WithdrawFee        float64 `json:"withdrawFee"`
 		EnableAutoWithdraw bool    `json:"enableAutoWithdraw"`
 	}
 	if err := c.ShouldBindJSON(&body); err != nil {
@@ -256,8 +271,9 @@ func AdminReferralSettingsPost(c *gin.Context) {
 	val := gin.H{
 		"distributorShare":   body.DistributorShare,
 		"minWithdrawAmount":  body.MinWithdrawAmount,
-		"bindingDays":        body.BindingDays,
-		"userDiscount":       body.UserDiscount,
+		"bindingDays":       body.BindingDays,
+		"userDiscount":      body.UserDiscount,
+		"withdrawFee":       body.WithdrawFee,
 		"enableAutoWithdraw": body.EnableAutoWithdraw,
 	}
 	valBytes, err := json.Marshal(val)