style: fix prefer-svelte-reactivity — replace with Svelte reactive equivalents

frontend/src/lib/components/admin/BookingCreateModal.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
 	import { authStore } from '$lib/stores/auth.svelte';
 	import { toast } from 'svelte-sonner';
-	import { SvelteDate } from 'svelte/reactivity';
+	import { SvelteDate, SvelteSet, SvelteURLSearchParams } from 'svelte/reactivity';
 	import { CalendarDate, getLocalTimeZone, type DateValue } from '@internationalized/date';
 	import { isValidUKPhone, toE164UK } from '$lib/utils/phone';
 	import { formatUserName } from '$lib/utils/nameDisplay';
@@ -235,7 +235,7 @@
 	// =============== Cache ===============
 	let workingHoursCache: Record<string, Record<string, DayHours>> = {};
 	let availableHoursCache: Record<string, Record<string, DayAvailability>> = {};
-	let loadingMonthKeys: Set<string> = new Set();
+	let loadingMonthKeys: Set<string> = new SvelteSet();
 
 	// =============== Derived Helpers ===============
 	function getTotalDuration() {
@@ -456,7 +456,7 @@
 		bookingCreateInitialLoadDone = false;
 		userNavigatedCalendar = false;
 		bookingCreateAutoSelectDone = false;
-		loadingMonthKeys = new Set();
+		loadingMonthKeys = new SvelteSet();
 		outOfHours = false;
 		normalWorkingHours = null;
 		// Clear reservation state
@@ -602,7 +602,7 @@
 
 		// Prevent re-entrant calls for the same month
 		if (loadingMonthKeys.has(monthKey)) return;
-		loadingMonthKeys = new Set(loadingMonthKeys).add(monthKey);
+		loadingMonthKeys = new SvelteSet(loadingMonthKeys).add(monthKey);
 
 		hoursMonthGeneration++;
 		const gen = hoursMonthGeneration;
@@ -657,7 +657,7 @@
 		} finally {
 			_loadingWorkingHours = false;
 			loadingAvailableHours = false;
-			loadingMonthKeys = new Set([...loadingMonthKeys].filter((k) => k !== monthKey));
+			loadingMonthKeys = new SvelteSet([...loadingMonthKeys].filter((k) => k !== monthKey));
 		}
 	}
 
@@ -811,7 +811,7 @@
 	async function fetchCustomServices() {
 		loadingCustomServices = true;
 		try {
-			const params = new URLSearchParams();
+			const params = new SvelteURLSearchParams();
 			if (customSearchQuery.trim()) {
 				params.set('q', customSearchQuery.trim());
 			} else {