feat(timeline): add pulse animation for in-flight drag mutations

Allocation bars that have active optimistic overrides (post-drag,
awaiting server confirmation) now pulse subtly via animate-pulse.
The pending set is derived from the existing optimisticAllocations
map keys, requiring no additional state.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/components/vacations/vacationExplainability.ts

@@ -1,5 +1,7 @@
 "use client";
 
+import { MILLISECONDS_PER_DAY } from "@capakraken/shared";
+
 export const HOLIDAY_SOURCE_LABELS = {
   CALENDAR: "Holiday Calendar",
   LEGACY_PUBLIC_HOLIDAY: "Legacy import",
@@ -32,7 +34,7 @@ export function getRequestedDays(vacation: Pick<VacationExplainabilityEntry, "st
 
   const start = new Date(vacation.startDate);
   const end = new Date(vacation.endDate);
-  return Math.round((end.getTime() - start.getTime()) / 86_400_000) + 1;
+  return Math.round((end.getTime() - start.getTime()) / MILLISECONDS_PER_DAY) + 1;
 }
 
 export function getHolidayBasis(vacation: VacationExplainabilityEntry): string[] {