- threshold.py: add _find_threshold() with suffix fallback so thresholds
like ping_monitor.rtt_avg match ping_monitor.8_8_8_8_rtt_avg etc.;
each pinged host keeps its own alert state
- hbdclass.py: format RTT as integer ms (round())
- live.html: JS RTT display rounded to nearest ms (Math.round)
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>