Method AddCommentAsync

backend/Services/TaskService.cs:437–483

(int taskId, string text, int userId)

    }

    public async Task<TaskActivityDto> AddCommentAsync(int taskId, string text, int userId)
    {
        if (!await VerifyTaskAccessAsync(taskId, userId))
            throw new UnauthorizedAccessException("User does not have access to this task.");

        var activity = new TaskActivity
        {
            TaskCardId = taskId,
            UserId = userId,
            Action = "Commented",
            Details = text,
            Timestamp = DateTime.UtcNow
        };

        _db.TaskActivities.Add(activity);
        await _db.SaveChangesAsync();

        Console.WriteLine($"[TaskService] Comment saved. ActivityId: {activity.Id}, TaskId: {taskId}, UserId: {userId}");

        // Detect mentions @username
        await DetectMentionsAsync(taskId, text, userId);

        // Load user info for the DTO
        var user = await _db.Users.AsNoTracking().FirstOrDefaultAsync(u => u.Id == userId);

        if (user == null)
        {
            Console.WriteLine($"[TaskService] WARNING: User not found in database for userId: {userId}");
        }
        else
        {
            Console.WriteLine($"[TaskService] User found: {user.Username} (ID: {user.Id})");
        }

        return new TaskActivityDto
        {
            Id = activity.Id,
            TaskCardId = activity.TaskCardId,
            UserId = activity.UserId,
            Username = user?.Username ?? "Unknown",
            UserAvatarUrl = user?.AvatarUrl,
            Action = activity.Action,
            Details = activity.Details,
            Timestamp = activity.Timestamp,
            Reactions = new List<ActivityReactionDto>()
        };
    }

    public async Task<TaskActivityDto?> UpdateActivityAsync(int activityId, string text, int userId)
    {