Upgraded to Lemmy 0.18.1

There was a bit of downtime. Upstream, lemmy had patched Nginx to not broadcast its version. We'd already done that anyway, and the duplicate directive caused downtime while I tracked down the error.

Sorry for the inconvenience.

Also, I reverted the default "theme" from our partizle-blue to Lemmy's default green because it works better for night mode users.