⚡ Bolt: [성능 개선] Daily Rollup 핫 경로 최적화

[seonghobae]

💡 What: Object.entries 대신 Object.keys를 사용하고, Set 할당을 반복문 밖으로 분리했습니다.
🎯 Why: 수백만 번의 반복이 발생할 수 있는 핫 경로에서 메모리 할당을 줄여 O(N*M) 성능 저하를 방지합니다.
📊 Impact: 가비지 컬렉터 부하를 대폭 낮추고 daily-rollup 및 통계 요약의 속도가 개선됩니다.
🔬 Measurement: pnpm test src/lib/server/daily-rollup.test.ts 통과 여부 및 Vercel 사용량 측정으로 확인 가능합니다.

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PR created automatically by Jules for task 7335714453902155971 started by @seonghobae

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