Apply Zero Padding to an Image

def zero_pad(
    image: list[list[list[int]]],
    pad: int,
) -> list[list[list[int]]]:
    """
    image: [H, W, C]
    pad: number of pixels to pad on each side
    """
    if pad <= 0:
        return [row[:] for row in image]

    H = len(image)
    W = len(image[0])
    C = len(image[0][0])

    new_H = H + 2 * pad
    new_W = W + 2 * pad

    # Create padded image filled with zeros
    padded = [[[0] * C for _ in range(new_W)] for _ in range(new_H)]

    # Copy original image into center
    for h in range(H):
        for w in range(W):
            for c in range(C):
                padded[h + pad][w + pad][c] = image[h][w][c]

    return padded