The base image never starts a service (closes #16)

build.sh and bin/test used to start valkey-server and ping it to prove it runs;
they now check it with valkey-server --version and valkey-cli --version, so the
ping loop, shutdown, and the cleanup of the Valkey run's log files are gone.
/var/log/valkey and /var/log/nginx keep their package owners and modes, and
nginx -t stays. README states that Valkey, PostgreSQL and nginx are installed
but never run. No package install starts a service: invoke-rc.d already denies
every start, and no ENTRYPOINT or CMD starts one.

Model: deepseek-v4-pro

README.md

@@ -1,9 +1,10 @@
 # baseimage
 
 A fat Docker base image that trades size for build speed. Everything a
-typical Go, Node, Python, or Hugo project needs is preinstalled. Child
-images only copy their source and build, without spending the first
-minutes of every build on `apt-get install` and toolchain downloads.
+typical Go, Node, Python, or Hugo project needs is preinstalled, so child
+images only have to copy their source and build, instead of spending the
+first few minutes of every build on `apt-get install` and toolchain
+downloads.
 
 Image: `git.eeqj.de/sneak/baseimage`, built for `linux/amd64` and
 `linux/arm64`.