- Add MetricsRetentionRawHours, MetricsRetentionMinuteHours, MetricsRetentionHourlyDays, MetricsRetentionDailyDays to SystemSettings
- Wire settings from system.json through Config to metrics store initialization
- Set sensible defaults: Raw=2h, Minute=24h, Hourly=7d, Daily=90d
- Log active retention values on startup for transparency
Users can now customize how long metrics are stored at each aggregation tier.
