⚡ Bolt: HexFormat 재사용을 통한 성능 개선

[seonghobae]

💡 What: java.util.HexFormat.of()를 매번 호출하는 대신 private static final 상수로 선언하여 재사용하도록 수정했습니다.
🎯 Why: 루프 또는 빈번하게 호출되는 메서드 내에서 HexFormat.of()를 반복적으로 호출하면 불필요한 중간 객체 할당이 발생하여 성능 저하와 GC(가비지 컬렉터) 오버헤드를 유발합니다.
📊 Impact: 16진수 문자열 변환 시 메모리 할당 감소 및 성능 향상
🔬 Measurement: mvn test 및 mvn org.jacoco:jacoco-maven-plugin:prepare-agent test org.jacoco:jacoco-maven-plugin:report 를 통해 기능 정상 동작 및 100% 테스트 커버리지 유지 확인

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PR created automatically by Jules for task 16912011006496599768 started by @seonghobae

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