Add nginx (closes #11)

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

Model: deepseek-v4-pro

bin/test

@@ -35,6 +35,7 @@ vips -l | grep -i heif > /dev/null
     valkey-server --version
     valkey-cli --version
     psql --version
+    nginx -v
     playwright --version
     firefox --version
     geckodriver --version