fix: fcmTokens eager로딩 관련 문제

[bingle625]

Eager loading can lead to performance issues, especially if the fcmTokens collection grows large. Consider using a JOIN FETCH in your queries or enabling hibernate.enable_lazy_load_no_trans with caution to avoid potential performance bottlenecks. This change could significantly degrade performance if not handled carefully.

Alternatively, consider using a DTO projection to only fetch the necessary data when needed. This approach can minimize the amount of data loaded into memory and improve query performance.

Is there a specific reason why lazy loading is causing issues? Understanding the root cause might lead to a more targeted solution.

See https://vladmihalcea.com/hibernate-facts-lazy-vs-eager-loading/ for more information.

Originally posted by @gemini-code-assist[bot] in #1004 (comment)