Feature/ha

[jkiddo]

• Added a small MQTT forwarder plus systemd wiring so a Pi can read the meter once at startup and then every 5 minutes and push results into Home Assistant.

• examples/home_assistant_mqtt.py: long-running helper that reads the meter serial once, then polls registers 60 68 80 74 86 87 266 every PYKMP_INTERVAL_SECONDS (default 300),
  publishing serial/state/per-register JSON to MQTT with optional HA discovery; config comes from env vars (MQTT_HOST, MQTT_* and PYKMP_*).
• contrib/systemd/pykmp-ha.env.example: sample env file for MQTT and meter settings (base topic, discovery toggle, poll interval).
• contrib/systemd/pykmp-ha-mqtt.service: systemd unit pointing at the helper script; adjust User/WorkingDirectory/ExecStart to your venv/repo path.
• docs/home-assistant-mqtt.md (+ nav entry in mkdocs.yml): step-by-step Raspberry Pi setup, install command (pip install ".[tool]" paho-mqtt), service install, and published
  topics.

Notes: paho-mqtt is an extra dependency; ensure the service user can access the serial device (dialout group). The script publishes discovery payloads to Home Assistant by
default.