Revaluate if backend should require tiffs to be in RGB/RGBA format before converting to PNG

[yousefmoazzam]

There's only a need for grayscale images in the frontend, so this conversion to RGB/RGBA is possibly unnecessary:

TomoHub/backend/routers/proxy.py

Lines 146 to 152 in f050ce3

	# Convert to RGB if necessary (TIFF might be in different modes)
	if img.mode not in ('RGB', 'RGBA'):
	if img.mode == 'I;16':
	array = np.array(img)
	normalized = (array.astype(np.uint16) - array.min()) * 255.0 / (array.max() - array.min())
	img = Image.fromarray(normalized.astype(np.uint8))
	img = img.convert('RGB')