#2 Issue 2: [IoT] MQTT Broker Integration

[elizabetheonoja-art]

Description:
The backend must talk to the hardware. Set up an MQTT broker (Mosquitto/AWS IoT) to listen for meter heartbeats.

Acceptance Criteria:

[ ] Subscribe to topic meters/+/status.

[ ] Publish to topic meters/{id}/command (Turn On/Off).

[ ] Handle connection drops gracefully.

Priority: Critical
Labels: iot, infrastructure