同步支持动态更新取件码长度，调整存量取件码以适配新长度并优化相关逻辑和文档。

internal/api/admin/config.go

@@ -4,6 +4,7 @@ import (
 	"FileRelay/internal/bootstrap"
 	"FileRelay/internal/config"
 	"FileRelay/internal/model"
+	"FileRelay/internal/service"
 	"net/http"
 
 	"github.com/gin-gonic/gin"
@@ -51,9 +52,21 @@ func (h *ConfigHandler) UpdateConfig(c *gin.Context) {
 		newConfig.Database.Path = config.GlobalConfig.Database.Path
 	}
 
+	// 检查取件码长度是否变化
+	pickupCodeLengthChanged := newConfig.Security.PickupCodeLength != config.GlobalConfig.Security.PickupCodeLength && newConfig.Security.PickupCodeLength > 0
+
 	// 更新内存配置
 	config.UpdateGlobalConfig(&newConfig)
 
+	// 如果长度变化，同步更新现有取件码
+	if pickupCodeLengthChanged {
+		batchService := service.NewBatchService()
+		if err := batchService.UpdateAllPickupCodes(newConfig.Security.PickupCodeLength); err != nil {
+			c.JSON(http.StatusInternalServerError, model.ErrorResponse(model.CodeInternalError, "Failed to update existing pickup codes: "+err.Error()))
+			return
+		}
+	}
+
 	// 重新初始化存储（热更新业务逻辑）
 	if err := bootstrap.ReloadStorage(); err != nil {
 		c.JSON(http.StatusInternalServerError, model.ErrorResponse(model.CodeInternalError, "Failed to reload storage: "+err.Error()))