Added MQTT topics for the new alarm duration control:
lva/<device_id>/alarm_duration/set
lva/<device_id>/alarm_duration/state
Published a new Home Assistant number discovery config:
number.<device_id>_alarm_duration (0–3600 seconds, step 5, unit s).
On /alarm_duration/set:
validates and parses the payload as a non-negative integer,
publishes a set_alarm_duration event on the EventBus,
echoes the value back to /alarm_duration/state.
On connect, publishes the current alarm_duration_seconds from preferences to the state topic for retained startup behavior.