perf(calendar): memoize recurring-event expansion (#982)

[DTriple-p]

Summary

Fixes #982: Memoizes recurring-event expansion in Calendar.tsx.

Context & Changes

Previously, events.flatMap(expandRecurring) was executed on every component render. Because expandRecurring performs up to 52 iterations per event, re-running this logic repeatedly was producing a new array instance identity on every render. This forced react-big-calendar to unnecessarily re-process events.

• Wrapped events.flatMap(expandRecurring) inside useMemo, with a dependency array keyed on events.

Verification

• Verified that recurring event expansion only recalculates when events changes.
• Checked TypeScript types and component structure.

[drips-wave]

@DTriple-p Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[RUKAYAT-CODER]

Thank you for contributing to the project.