docs(deps): update OpenSSL requirement to 3.0+ in build guides

Remove OpenSSL 1.1.1 backward compatibility notes and security warnings
from BUILD_GUIDE.md and BUILD_GUIDE.kr.md. OpenSSL 3.0+ is now the only
supported version for PostgreSQL SSL connections.

Author: kcenon

docs/guides/BUILD_GUIDE.kr.md

@@ -30,14 +30,12 @@
 
 데이터베이스 지원은 선택 사항이며 테스트를 위해 비활성화할 수 있습니다:
 
-- **PostgreSQL**: libpqxx, libpq, OpenSSL 3.x (권장) 또는 1.1.1 (지원 중단)
+- **PostgreSQL**: libpqxx, libpq, OpenSSL 3.0+
 - **MySQL**: libmysql 또는 mysql-connector-cpp
 - **SQLite**: sqlite3
 - **MongoDB**: mongo-cxx-driver (mongocxx, bsoncxx)
 - **Redis**: hiredis
 
-> **⚠️ 보안 참고**: OpenSSL 1.1.1은 2023년 9월에 지원이 종료되었습니다. 하위 호환성을 위해 여전히 지원되지만, 지속적인 보안 패치를 위해 OpenSSL 3.x로 업그레이드하는 것을 강력히 권장합니다.
-
 ## 빠른 시작
 
 ### 1. 저장소 클론

docs/guides/BUILD_GUIDE.md

@@ -30,14 +30,12 @@ Comprehensive guide for building the Database System with multi-backend support,
 
 Database support is optional and can be disabled for testing:
 
-- **PostgreSQL**: libpqxx, libpq, OpenSSL 3.x (recommended) or 1.1.1 (deprecated)
+- **PostgreSQL**: libpqxx, libpq, OpenSSL 3.0+
 - **MySQL**: libmysql or mysql-connector-cpp
 - **SQLite**: sqlite3
 - **MongoDB**: mongo-cxx-driver (mongocxx, bsoncxx)
 - **Redis**: hiredis
 
-> **⚠️ Security Note**: OpenSSL 1.1.1 reached End-of-Life in September 2023. While still supported for backward compatibility, upgrading to OpenSSL 3.x is strongly recommended for continued security patches.
-
 ## Quick Start
 
 ### 1. Clone Repository