fix: remove redundant rollback, document asymmetry in cancellation notifications

backend/handlers/today/today.go

@@ -322,7 +322,7 @@ func computeAggregateSummary(r *http.Request, rangeStart, rangeEnd time.Time) *D
 		) sub ON true
 		WHERE b.start_time >= $1 AND b.start_time < $2
 	`
-	_ = db.Conn.QueryRow(r.Context(), query, rangeStart, rangeEnd).Scan(
+	if err := db.Conn.QueryRow(r.Context(), query, rangeStart, rangeEnd).Scan(
 		&summary.TotalPaymentsToday,
 		&summary.TotalTipsToday,
 		&summary.TotalVATCollected,
@@ -335,7 +335,9 @@ func computeAggregateSummary(r *http.Request, rangeStart, rangeEnd time.Time) *D
 		&summary.LastCustomerName,
 		&summary.LastCustomerVisits,
 		&summary.GuestCustomers,
-	)
+	); err != nil {
+		log.Printf("Failed to scan today summary: %v", err)
+	}
 
 	// Customers served = new + returning + guest (distinct people, not bookings)
 	summary.CustomersServed = summary.NewCustomers + summary.ReturningCustomers + summary.GuestCustomers