[Question] <Could you please confirm if this alert logic is supported: Trigger an alarm if no data is received within 90 seconds (for example)?>

### Question

Could you please confirm if this alert logic is supported: Trigger an alarm if no data is received within 90 seconds (for example)?

The issue names no file, test, or entry point. Start by checking HertzBeat's existing alerting documentation and configuration behavior for missing data, then confirm whether a 90-second no-data alarm is supported and document the answer or define the required change.

Written by the indexing model from the issue text.