- Create Alembic migration 035 with site_alert_rules and site_alert_events tables, RLS policies, and GRANT
- Add SiteAlertRule/SiteAlertEvent ORM models with enums for rule_type, severity, state
- Add Pydantic schemas for rule/event CRUD and signal history points
- Add SIGNAL_DEGRADATION_THRESHOLD_DB, ALERT_EVALUATION_INTERVAL_SECONDS, TREND_DETECTION_INTERVAL_SECONDS to Settings
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>