[FRONTEND] Turn the exit confirmation dialog into our implementation of window.confirm

[bcho892]

Is your feature request related to a problem? Please describe.

Right now we have a lot of occurrences where we use if(confirm()). This is good but doesn't allow a custom design. We should make it so that we can just use a drop-in replacement

BEFORE MERGING

• [ ] Storybooks created where possible
• [ ] Tested with nock if data fetching
• [ ] Tests written for critical interactions
• [ ] PR Reviewed (For non-trivial changes)
• [ ] Changes tested after rebasing on master or merging in master (hint: git fetch origin master:master, then git rebase master or git merge master)
• [ ] All required PR checks passing