ipabusedb-docker-ssh: autoload .env via godotenv, document DOCKER_HOST passthrough, surface docker CLI errors

ipabusedb-docker-ssh/.env.example

@@ -0,0 +1,5 @@
+# Copy to .env (gitignored). Variables already set in your shell win.
+IPABUSEDB_API_KEY=
+DOCKER_CONTAINER_NAME=sshd
+# Point the docker CLI at a remote daemon; credentials above stay local.
+DOCKER_HOST=ssh://user@sshd-host.example.com