Add a writeback device to zram0 #247
Description
Switching to zram swap as per #245 has been great for server performance and stability. But RAM is still limited; I would sleep better knowing that we had 1GiB of on-disk swap as spillover, just in case. zram swap can be configured to writeback to a block device, but not on Alma Linux 9 — we'll need a newer kernel first. Accordingly, this is blocked until we are on Alma Linux 10. (#243)