Duplicate calendar

[jotalis]

Summary

• Copy to New Schedule functionality
• Enforce unique schedule names when duplicating, creating, or renaming a schedule
• Fix bug where schedule names aren't updated and thus displayed properly for deletion modals

Test Plan

• Undo New Schedule Creation: Verify undo functionality removes a newly created schedule.
• Combined Undo for Schedule Creation and Event Copying: Confirm one undo removes both a new schedule and copied events.
• Duplicate Schedule Name on Creation: Validate a duplicate schedule name results in a suffix like (1).
• Duplicate Schedule Name on Renaming: Check renaming to an existing name adds a suffix or prevents duplication.
• Renaming and Duplicating Schedules: Verify renaming a schedule and duplicating it results in proper suffixes.
• Adding Custom Events: Verify custom events are added with all details intact.
• Start with existing schedule 2025-Winter. Create new schedule with same name. Expect 2025-Winter(1). Try renaming schedule to 2025-Winter. Expect 2025-Winter(1)
• Deleting schedule modal shows correct name of schedule to delete; Create 3 schedules; delete the second schedule; open up the delete modal for the third schedule. It should display the name of the third schedule and not the second schedule

Issues

Closes #1034, #1032

[MinhxNguyen7]

While you're here, can you replace the dropdown with a list of buttons? There's no reason to select, then having to press a button.

[KevinWu098]

Congrats on your first PR! Looks solid, barring one issue I've noted below.

[jotalis]

Update: discussed with AA team to prioritize a simpler and more familiar duplication functionality (e.g. Make a Copy from Google Docs). The copy schedule modal is now only going to allow the making of duplicate schedules, removing "Copy to All Schedules" and "Copy to Schedule".

[jotalis]

Currently when the user tries to duplicate a schedule, a unique schedule name is enforced upon schedule creation, even if what they enter already exists.

For example, if Winter-2025 exists, and a schedule tries to be duplicated with the name Winter-2025, a number (e.g. (1)) will be appended to the schedule name upon creation.

However, users are still able to have schedule with duplicate names in these cases:

1. They have existing schedules with duplicate names already
2. They rename a schedule to an already existing schedule name
3. They create a new schedule using an already existing schedule name

To help migrate towards a system where all schedule names are unique, we should enforce the same naming validation in the duplicate schedule feature for 2 and 3 (renaming and creating schedules).

[KevinWu098]

LGTM! 🚀

2 non-blocking questions for you, but otherwise, it looks good to merge

[MinhxNguyen7]

If this breaks prod, I blame @KevinWu098