Decline feature

[Invictus108]

Adds a decline button so users can indicate if they don't want to go to the event

This will later be used for email reminders and invitations

It will modify the Firebase schema as it goes, adding a isdeclined boolean field

[github-actions]

Visit the preview URL for this PR (updated for commit db1e431):

https://studybuddy-392c7--pr-360-6gdofp79.web.app

_{(expires Tue, 14 Apr 2026 01:14:42 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: 1e823c805395bb7b968e98b8401ce59756126c01}

[rylany27]

A few things:

1. An admin shouldn't have the option to decline an invitation
2. Only the admin should be able to see who's declined (for now, makes the rest easier)
3. Once a participant declines, they should be redirected to the landing page, and the event should be removed from that user's firebase (they should still be able to access the same event via the dashboard link as before)
4. On the admin's side, if a declined participant rejoins the event and fills out their availability, the declined status should be removed
5. There should be a confirm to decline popup (feel free to reuse the confirm to delete event one)

[Invictus108]

Ok I think I got all of the changes. Let me know if there is anything else

[rylany27]

Looks good I think. One more thing I ran into is that there's a Firebase error when trying to decline an invitation as a guest. I think it'd be simplest to just remove the option entirely for guests.

(it might be worth discussing in the future phasing out guest accounts entirely)

[Invictus108]

sorry about that. Fixed it