前端：

1、优化消息排序逻辑
2、新增加载历史消息
3、修复已知问题
后端：
1、优化消息排序逻辑
2、增加用户信息缓存机制
3、修改日期类型为DateTimeOffset改善时区信息丢失问题
3、修复了已知问题
数据库：
1、新增SequenceId字段用于消息排序
2、新增ClientMsgId字段用于客户端消息回执

backend/IM_API/Services/AuthService.cs

@@ -14,15 +14,19 @@ namespace IM_API.Services
         private readonly ImContext _context;
         private readonly ILogger<AuthService> _logger;
         private readonly IMapper _mapper;
-        public AuthService(ImContext context, ILogger<AuthService> logger, IMapper mapper)
+        private readonly ICacheService _cache;
+        public AuthService(ImContext context, ILogger<AuthService> logger, IMapper mapper, ICacheService cache)
         {
             _context = context;
             _logger = logger;
             _mapper = mapper;
+            _cache = cache;
         }
 
         public async Task<User> LoginAsync(LoginRequestDto dto)
         {
+            var userinfo = await _cache.GetUserCacheAsync(dto.Username);
+            if (userinfo != null && userinfo.Password == dto.Password) return userinfo;
             string username = dto.Username;
             string password = dto.Password;
             var user = await _context.Users.FirstOrDefaultAsync(x => x.Username == username && x.Password == password);
@@ -30,6 +34,7 @@ namespace IM_API.Services
             {
                 throw new BaseException(CodeDefine.PASSWORD_ERROR);
             }
+            await _cache.SetUserCacheAsync(user);
             return user;
         }