[Refactor] Review and improve configurations

[nkcoder]

Summary

Review and improve the configs (application.yml, .env).s

Type of Change

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature causing existing functionality to not work as expected)
• Refactoring (no functional changes)
• Documentation update

Changes Made

• application.yml: env config with default value
• application-{env}.yml: override env-specific values
• .env: environment variables

Checklist

• Code follows project style guidelines
• Self-review completed
• Tests added for new functionality
• Documentation updated (if needed)

Reviewer Notes

N/A