Feature: Multi-email alerts and move resource between groups

- notificationService: Parse comma-separated emails from resource.email_to or global config; validate and send to each recipient
- API: Add PATCH /api/resources/:id/group endpoint to move resource between groups with validation and cache invalidation
- UI: Add group selector to edit modal; wire group change to PATCH endpoint; add help text for multi-email format

server/database.js

@@ -113,8 +113,9 @@ db.exec(`
 
   CREATE INDEX IF NOT EXISTS idx_checks_resource_id ON checks(resource_id);
   CREATE INDEX IF NOT EXISTS idx_checks_checked_at ON checks(checked_at);
-  CREATE INDEX IF NOT EXISTS idx_checks_resource_checked ON checks(resource_id, checked_at DESC);
+  CREATE INDEX IF NOT EXISTS idx_checks_resource_checked ON checks(resource_id, checked_at);
   CREATE INDEX IF NOT EXISTS idx_incidents_resource_id ON incidents(resource_id);
+  CREATE INDEX IF NOT EXISTS idx_incidents_resource_started ON incidents(resource_id, started_at);
   CREATE INDEX IF NOT EXISTS idx_incidents_resolved ON incidents(resource_id, resolved_at);
   CREATE INDEX IF NOT EXISTS idx_resources_group_id ON resources(group_id);
   CREATE INDEX IF NOT EXISTS idx_maintenance_windows_resource ON maintenance_windows(resource_id);