Add a `LastAlertDetection` module for SMARTCAM devices exposing `getLastAlarmInfo` as two `Info` sensor features:
- `last_alert_timestamp` — tz-aware `datetime` of the last alert, `None` when the device has never detected anything (`last_alarm_time` is `""` or `"0"` on such devices, and an unexpected value is also mapped to `None`
- `last_alert_type` — `LastAlertType` enum (`Motion`; `Unknown` fallback with a one-time warning per unknown raw value), `None` when unset.
