fix: 修复权限组用户看不到实例的bug — AccessibleInstances第二次Pluck覆盖第一次结果，改为单条OR查询

backend/internal/handler/instance_extra.go

@@ -34,19 +34,10 @@ func AccessibleInstances(c *gin.Context) {
 			return
 		}
 		var instanceIDs []int
+		// Query for the requested access_type OR readwrite (readwrite grants both)
 		model.DB.Model(&model.InstanceGroupMember{}).
-			Where("group_id IN ? AND access_type = ?", groupIDs, accessType).
+			Where("group_id IN ? AND (access_type = ? OR access_type = ?)", groupIDs, accessType, "readwrite").
 			Pluck("instance_id", &instanceIDs)
-		// also include readwrite
-		if accessType == "readonly" {
-			model.DB.Model(&model.InstanceGroupMember{}).
-				Where("group_id IN ? AND access_type = ?", groupIDs, "readwrite").
-				Pluck("instance_id", &instanceIDs)
-		} else if accessType == "write" {
-			model.DB.Model(&model.InstanceGroupMember{}).
-				Where("group_id IN ? AND access_type = ?", groupIDs, "readwrite").
-				Pluck("instance_id", &instanceIDs)
-		}
 		if len(instanceIDs) == 0 {
 			c.JSON(http.StatusOK, []model.Instance{})
 			return