refactor: use date-fns for dashboard dates

src/routes/dashboard/+page.server.ts

@@ -1,3 +1,4 @@
+import { addDays, addMonths, endOfMonth, format, parseISO, startOfMonth } from 'date-fns';
 import { and, asc, count, desc, eq, gte, inArray, isNull, lt, lte, ne, sql } from 'drizzle-orm';
 import { db } from '$lib/server/db';
 import {
@@ -12,42 +13,20 @@ import {
 import { loadOrganizationContext } from '$lib/server/organizations';
 import type { PageServerLoad } from './$types';
 
-const dayMs = 24 * 60 * 60 * 1000;
-
-function pad(value: number) {
-	return String(value).padStart(2, '0');
-}
-
 function dateOnly(date: Date) {
-	return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}`;
+	return format(date, 'yyyy-MM-dd');
 }
 
 function dateTimeLocal(date: Date) {
-	return `${dateOnly(date)}T${pad(date.getHours())}:${pad(date.getMinutes())}`;
-}
-
-function startOfMonth(date: Date) {
-	return new Date(date.getFullYear(), date.getMonth(), 1);
-}
-
-function endOfMonth(date: Date) {
-	return new Date(date.getFullYear(), date.getMonth() + 1, 0);
-}
-
-function addDays(date: Date, days: number) {
-	return new Date(date.getTime() + days * dayMs);
-}
-
-function addMonths(date: Date, months: number) {
-	return new Date(date.getFullYear(), date.getMonth() + months, 1);
+	return format(date, "yyyy-MM-dd'T'HH:mm");
 }
 
 function monthKey(date: Date) {
-	return `${date.getFullYear()}-${pad(date.getMonth() + 1)}`;
+	return format(date, 'yyyy-MM');
 }
 
 function monthLabel(date: Date) {
-	return new Intl.DateTimeFormat('en-GB', { month: 'short', year: 'numeric' }).format(date);
+	return format(date, 'MMM yyyy');
 }
 
 function roomTypeLabel(type: string) {
@@ -323,7 +302,7 @@ export const load: PageServerLoad = async ({ locals }) => {
 		});
 	}
 	for (const invoice of billingTrendInvoiceRows) {
-		const issuedAt = new Date(`${invoice.issueDate}T00:00:00`);
+		const issuedAt = parseISO(invoice.issueDate);
 		const key = monthKey(issuedAt);
 		const existing = billingTrendMap.get(key);
 		if (!existing) continue;