- Add numeric_value, numeric_min, numeric_max fields to stat_minutely, stat_hourly, stat_daily tables
- Modify UptimeCalculator to aggregate numeric values instead of storing directly
- Update monitor.js and SNMP monitor to pass numeric values to uptime calculator
- Update chart handler to query from aggregated stat tables instead of monitor_numeric_history
- Add cleanup logic for monitor_numeric_history table (keeps last 7 days for transition)
- Fixes GC issue where monitor_numeric_history table was never cleaned up
- Prevents UI performance issues for long-running monitors
