Method UpdateTaskAsync

backend/Services/ITaskService.cs:9–9

(int taskId, UpdateTaskDto dto, int userId)

{
    Task<TaskCardDto> CreateTaskAsync(CreateTaskDto dto, int userId);
    Task<TaskCardDto?> UpdateTaskAsync(int taskId, UpdateTaskDto dto, int userId);
    Task<TaskCardDto?> MoveTaskAsync(int taskId, MoveTaskDto dto, int userId);
    Task<int?> DeleteTaskAsync(int taskId, int userId); // Returns BoardId if successful