fix: booking duration calculation, tip page auth, and UI polish across frontend

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/handlers/bookings/bookings.go

@@ -2323,8 +2323,10 @@ func ConfirmBookingHandler(w http.ResponseWriter, r *http.Request) {
 	if dav.Service != nil {
 		var durationMinutes int
 		db.DB.QueryRow(r.Context(), `
-			SELECT COALESCE(SUM(override_duration_minutes), (SELECT SUM(duration_minutes) FROM booking_services WHERE booking_id = $1))
-			FROM booking_services WHERE booking_id = $1
+			SELECT COALESCE(SUM(COALESCE(bs.override_duration_minutes, s.duration_minutes)), 60)
+			FROM booking_services bs
+			JOIN services s ON bs.service_id = s.id
+			WHERE bs.booking_id = $1
 		`, bookingID).Scan(&durationMinutes)
 		if durationMinutes == 0 {
 			durationMinutes = 60