IAV-88/feat: initial project setup with base structure and configuration files

🎯 Overview

This MR initializes the base project structure for the IAVIA File Manager Service microservice.

📋 Changes

• ✅ Created Spring Boot project structure with clean architecture layers
• ✅ Set up package organization:
  • configs - Application configuration classes
  • constants - Application constants
  • controllers - REST API controllers
  • dtos - Data Transfer Objects
  • mappers - Entity/DTO mappers
  • repositories - Data access layer
  • services - Business logic layer
  • utils - Utility classes
• ✅ Added Docker support (Dockerfile + docker-compose.yml)
• ✅ Configured GitLab CI/CD pipeline (.gitlab-ci.yml)
• ✅ Added project documentation (README.md, CHANGELOG.md)
• ✅ Set up Maven configuration (pom.xml)
• ✅ Added .gitignore for Java/Maven projects

📝 Notes

• This is the foundation for the file manager service
• Ready for feature development
• All standard configurations are in place

Closes IAV-88