Add maintenance windows for planned work

store.go

@@ -147,6 +147,9 @@ func openStore(path string) (*Store, error) {
 	}
 	// Older databases get this column without requiring a separate migration tool.
 	_, _ = db.Exec(`ALTER TABLE alert_events ADD COLUMN recovery_sent_at INTEGER`)
+	_, _ = db.Exec(`ALTER TABLE alert_events ADD COLUMN planned INTEGER NOT NULL DEFAULT 0`)
+	_, _ = db.Exec(`ALTER TABLE alert_events ADD COLUMN maintenance_reason TEXT NOT NULL DEFAULT ''`)
+	_, _ = db.Exec(`DELETE FROM alert_events WHERE alert_key='monitor-slow'`)
 	_, _ = db.Exec(`ALTER TABLE service_checks ADD COLUMN endpoint TEXT NOT NULL DEFAULT 'public'`)
 	_, _ = db.Exec(`PRAGMA foreign_keys=ON`)
 	return &Store{db: db, path: path}, nil