[WIP] Update 회원가입 로직 수정 for useMemo optimization

[Copilot]

Thanks for the feedback on #11. I've created this new PR, which merges into #11, to address your comment. I will work on the changes and keep this PR's description up to date as I make progress.

Original PR: #11
Triggering review: #11 (comment)

@copilot open a new pull request to apply changes based on this feedback
In this project, we are using the React Compiler, so this kind of calculation is automatically memoized by the compiler.
Since the filtering logic is a pure computation that depends only on universityName and universityList, React Compiler can safely optimize it without needing an explicit useMemo.

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