Method CreateColumnAsync

backend/Services/BoardService.cs:634–672

(int boardId, CreateColumnDto dto, int userId)

    }

    public async Task<ColumnDto> CreateColumnAsync(int boardId, CreateColumnDto dto, int userId)
    {
        // 1. Verify user has access (Owner or Member)
        var board = await _db.Boards
            .Include(b => b.Members)
            .Include(b => b.Workspace).ThenInclude(w => w.Members)
            .Include(b => b.Columns) // Include columns to calculate Order
            .FirstOrDefaultAsync(b => b.Id == boardId);

        if (board == null) throw new KeyNotFoundException("Board not found");

        var isMember = board.OwnerId == userId
            || board.Members.Any(m => m.UserId == userId && m.Status == "Accepted")
            || (board.Workspace != null && board.Workspace.Members.Any(wm => wm.UserId == userId && wm.Status == "Accepted"));

        if (!isMember) throw new UnauthorizedAccessException("User is not a member of this board");

        // 2. Calculate Order
        var maxOrder = board.Columns.Any() ? board.Columns.Max(c => c.Order) : -1;

        // 3. Create Column
        var column = new Column
        {
            Name = dto.Name,
            BoardId = boardId,
            Order = maxOrder + 1
        };

        _db.Columns.Add(column);
        await _db.SaveChangesAsync();

        return new ColumnDto
        {
            Id = column.Id,
            Name = column.Name,
            Order = column.Order,
            TaskCards = new List<TaskCardDto>()
        };
    }

    public async Task<bool> MoveColumnAsync(int boardId, int columnId, int newOrder, int userId)
    {