Add environment variable example and update .gitignore

- Created a new .env.example file to provide a template for environment variables, including database connection details, JWT settings, encryption keys, and external API keys.
- Updated .gitignore to include additional test output directories and archive files, ensuring that unnecessary files are not tracked by Git.
- Removed outdated approval test reports and scripts that are no longer needed, streamlining the project structure.

These changes improve the clarity of environment configuration and maintain a cleaner repository.

docker/dev/docker-compose.backend.mac.yml

@@ -12,15 +12,15 @@ services:
     environment:
       - NODE_ENV=development
       - PORT=8080
-      - DATABASE_URL=postgresql://postgres:ph0909!!@39.117.244.52:11132/plm
-      - JWT_SECRET=ilshin-plm-super-secret-jwt-key-2024
-      - JWT_EXPIRES_IN=24h
+      - DATABASE_URL=${DATABASE_URL}
+      - JWT_SECRET=${JWT_SECRET}
+      - JWT_EXPIRES_IN=${JWT_EXPIRES_IN:-24h}
       - CORS_ORIGIN=http://localhost:9771
       - CORS_CREDENTIALS=true
       - LOG_LEVEL=debug
-      - ENCRYPTION_KEY=ilshin-plm-mail-encryption-key-32characters-2024-secure
-      - KMA_API_KEY=ogdXr2e9T4iHV69nvV-IwA
-      - ITS_API_KEY=d6b9befec3114d648284674b8fddcc32
+      - ENCRYPTION_KEY=${ENCRYPTION_KEY}
+      - KMA_API_KEY=${KMA_API_KEY}
+      - ITS_API_KEY=${ITS_API_KEY}
       - EXPRESSWAY_API_KEY=${EXPRESSWAY_API_KEY:-}
     volumes:
       - ../../backend-node:/app # 개발 모드: 코드 변경 시 자동 반영