chore: gitignore에 CSV 파일 추가

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: hchang

.gitignore

@@ -46,3 +46,7 @@ next-env.d.ts
 # Misc
 .turbo
 certs/
+
+# Sensitive data
+*.csv
+사전등록자.csv