Follow-ups from the capture-reliability review:
- All server-side capture log lines are now prefixed with a local
timestamp (YYYY-MM-DD HH:MM:SS) for easier correlation.
- New --log-interval SECONDS CLI flag (default 60) tunes the
"Capture alive" heartbeat interval; passed through to CaptureManager.
Stays on 1.22.0 (backend-only). 369 tests pass.