fix: metric samples timestamp + ssh-script port/user handling

- InsertMetricSample now includes ts=now() (TimescaleDB hypertable requires it)
- ssh-script: pass host and port separately (ssh uses -p flag, not host:port)
- ssh-script: use OIKOS_SSH_USER from config/env, default root
- Add -o LogLevel=ERROR to suppress SSH warnings polluting JSON output
- Use Output() (stdout only) instead of CombinedOutput()
- Set OIKOS_SSH_USER=root in scheduler docker-compose service

docker-compose.yml

@@ -84,6 +84,7 @@ services:
       OIKOS_DEBUG: "true"
       OIKOS_SCHEDULER_INTERVAL: "30s"
       OIKOS_SSH_KEY_PATH: /etc/oikos/ssh_key
+      OIKOS_SSH_USER: root
     volumes:
       - ${OIKOS_SSH_KEY_PATH:-~/.ssh/id_ed25519}:/etc/oikos/ssh_key:ro
     cap_add: