前端：

1、更新界面图标
2、修改消息缓存逻辑
3、新增清空未读消息数
后端：
1、修复不同时区导致的时间显示问题
2、新增清空未读消息数接口

backend/IM_API/Configs/MapperConfig.cs

@@ -41,7 +41,7 @@ namespace IM_API.Configs
             CreateMap<FriendRequestDto, FriendRequest>()
                 .ForMember(dest => dest.RequestUser , opt => opt.MapFrom(src => src.FromUserId))
                 .ForMember(dest => dest.ResponseUser , opt => opt.MapFrom(src => src.ToUserId))
-                .ForMember(dest => dest.Created , opt => opt.MapFrom(src => DateTime.Now))
+                .ForMember(dest => dest.Created , opt => opt.MapFrom(src => DateTime.UtcNow))
                 .ForMember(dest => dest.StateEnum , opt => opt.MapFrom(src => FriendRequestState.Pending))
                 .ForMember(dest => dest.Description , opt => opt.MapFrom(src => src.Description))
                 ;
@@ -101,7 +101,7 @@ namespace IM_API.Configs
                 .ForMember(dest => dest.TargetId, opt => opt.MapFrom(src => src.MsgRecipientId))
                 .ForMember(dest => dest.UnreadCount, opt => opt.MapFrom(src => 0))
                 .ForMember(dest => dest.StreamKey, opt => opt.MapFrom(src => src.StreamKey))
-                .ForMember(dest => dest.LastMessageTime, opt => opt.MapFrom(src => DateTime.Now))
+                .ForMember(dest => dest.LastMessageTime, opt => opt.MapFrom(src => DateTime.UtcNow))
                 ;
 
             //创建会话对象