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- Removed outdated approval test reports and scripts that are no longer needed, streamlining the project structure.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.

backend-node/src/config/environment.ts

@@ -93,7 +93,7 @@ const config: Config = {
 
   // JWT 설정
   jwt: {
-    secret: process.env.JWT_SECRET || "ilshin-plm-super-secret-jwt-key-2024",
+    secret: process.env.JWT_SECRET || "change-this-jwt-secret-in-env",
     expiresIn: process.env.JWT_EXPIRES_IN || "24h",
     refreshExpiresIn: process.env.JWT_REFRESH_EXPIRES_IN || "7d",
   },