style: fix prefer-const and prettier formatting issues

frontend/src/lib/components/today/TodayCalendar.svelte

@@ -28,7 +28,7 @@
 		openUserModal: (userId: string) => void;
 	}
 
-	let { openBookingModal, openUserModal }: Props = $props();
+	const { openBookingModal, openUserModal }: Props = $props();
 
 	type TodayAppointment = {
 		id: string;
@@ -155,7 +155,7 @@
 		return blocker.description?.startsWith('RESERVATION:') ?? false;
 	}
 
-	let availableStartOptions = $derived.by(() => {
+	const availableStartOptions = $derived.by(() => {
 		const wh = workingHours;
 		if (!wh || !wh.isOpen) return [];
 		const startMin = timeToMinutes(wh.startTime);
@@ -174,7 +174,7 @@
 		return options;
 	});
 
-	let availableEndOptions = $derived.by(() => {
+	const availableEndOptions = $derived.by(() => {
 		const wh = workingHours;
 		if (!wh || !wh.isOpen) return [];
 		const endMin = timeToMinutes(wh.endTime);
@@ -197,7 +197,7 @@
 		return options;
 	});
 
-	let suggestedLunch = $derived.by(() => {
+	const suggestedLunch = $derived.by(() => {
 		if (!workingHours || !availableHours || !workingHours.isOpen) return null;
 		const wh = workingHours;
 		const ah = availableHours;
@@ -284,7 +284,7 @@
 		| LunchTimelineItem
 		| ClosingTimeTimelineItem;
 
-	let timeline = $derived.by(() => {
+	const timeline = $derived.by(() => {
 		const items: TimelineItem[] = [];
 
 		for (const apt of appointments) {
@@ -512,7 +512,7 @@
 		return formatLocalDateTime(dt);
 	}
 
-	let canCreate = $derived.by(() => !hasOverlap && !checkingOverlap);
+	const canCreate = $derived.by(() => !hasOverlap && !checkingOverlap);
 
 	async function createBlocker() {
 		if (!canCreate) return;