Add nginx (closes #11)

Install nginx from apt and check nginx -t in the smoke test.

Model: deepseek-v4-pro

bin/test

@@ -39,6 +39,7 @@ docker run --rm "$img" bash -ec '
     valkey-cli shutdown nosave
     psql --version
     postgres --version
+    nginx -t
     playwright --version
     firefox --version
     geckodriver --version