The energy-cost device has only sensors (no online/offline heartbeat), but the
discovery config still declared an availability topic that nothing ever publishes
'online' to — so Home Assistant marked every energy-cost entity 'unavailable'
even though the state topic was being published (visible in MQTT Explorer).
- DeviceInfo gains provides_availability (default True, keeps Modbus behavior).
- _energy_cost_provider sets provides_availability=False.
- build_discovery_payload only emits availability/availability_mode for devices
that publish a heartbeat; HA treats the rest as always-available.
- Test asserts energy-cost configs omit availability.
Config hot-reload (no restart):
- MqttManager.unsubscribe(); apply_dsmr_subscription(settings) re-applies the
DSMR subscription (subscribe/unsubscribe/topic-change, fresh snapshot so the
sample interval also takes effect).
- Called from lifespan AND PUT /api/config, so toggling DSMR ingest in the UI
takes effect immediately without restarting the app.
Decouple ingest from the DSMR telegram id (overflows / resets to zero):
- Migration 20260624_12: drop UNIQUE(source_id), make recorded_at UNIQUE.
- Idempotency now keys on recorded_at (telegram timestamp); the table's own
autoincrement PK is the stable identity. source_id kept only as a reference.
- Regression test: colliding telegram ids no longer drop new data.
tliu93