Fix Infinity validation in addDaysToDateKey

The function only checked for NaN, not Infinity. If the date string represented
an extreme date, getTime() could return Infinity, causing the date arithmetic
to produce invalid results.

Changed Number.isNaN() to Number.isFinite() to catch both NaN and Infinity.

Author: pavankumar-vh

common/src/util/freebuff-streak.ts

@@ -48,7 +48,7 @@ export function getFreebuffUsageDateKey(
 
 export function addDaysToDateKey(dateKey: string, days: number): string {
   const date = new Date(`${dateKey}T00:00:00.000Z`)
-  if (Number.isNaN(date.getTime())) {
+  if (!Number.isFinite(date.getTime())) {
     throw new Error(`Invalid date key: ${dateKey}`)
   }