- Add database model for storing AMS sensor history (humidity, temperature)
- Record sensor data every 5 minutes via background task
- Add API endpoint to retrieve history with min/max/avg statistics
- Create AMSHistoryModal component with Recharts line charts
- Make humidity/temperature indicators clickable to open history
- Support time range selection (6h, 24h, 48h, 7d)
- Show threshold reference lines on charts (Good/Fair levels)
- Add configurable data retention (default 30 days) in Settings
- Auto-cleanup old data daily
- Fix dark theme styling in modal using inline styles
- Add Escape key to close modal