fix: merge lunch-blocked slots into single unavailable group

- generateGroupedTimeSlots now accepts lunchProtection map parameter
- Lunch-blocked slots treated as unavailable during grouping, not after
- Consecutive lunch-blocked slots merge into one unavailable button
- Admin BookingCreateModal already had this fix; BookingFlow now matches

frontend/src/lib/components/booking/BookingFlow.svelte

@@ -499,7 +499,8 @@
 
 	function generateGroupedTimeSlots(
 		duration: number,
-		date: CalendarDate | undefined
+		date: CalendarDate | undefined,
+		lunchProtection: Map<string, { isBlocked: boolean; showWarning: boolean; warningMessage?: string }> = new Map()
 	): Array<{
 		type: 'available' | 'unavailable';
 		startTime: string;
@@ -549,7 +550,7 @@
 			const minute = minutes % 60;
 			const timeStr = `${String(hour).padStart(2, '0')}:${String(minute).padStart(2, '0')}`;
 
-			const isAvailable = availableSlots.includes(timeStr);
+			const isAvailable = availableSlots.includes(timeStr) && !lunchProtection.get(timeStr)?.isBlocked;
 
 			if (isAvailable) {
 				if (currentUnavailableStart !== null) {
@@ -749,7 +750,7 @@
 	const formattedTotalDuration = $derived(formatDuration(getTotalDuration()));
 	const groupedTimeSlots = $derived(
 		currentStep === 2 && selectedServices.length > 0 && selectedDate
-			? generateGroupedTimeSlots(getTotalDuration(), selectedDate)
+			? generateGroupedTimeSlots(getTotalDuration(), selectedDate, lunchProtectionStatus())
 			: []
 	);
 	const formattedSelectedDate = $derived(