Add API Server Implementation with Echo Framework

[yanosea]

Current Status

• The application lacks a proper API server implementation
• No endpoints are available for client interaction
• Missing framework for handling HTTP requests efficiently

Expected Changes

• Implement API server using Echo framework
• Create configuration handling for the API server
• Add endpoint to return random Japanese phrases
• Implement proper testing setup with mock objects

Expected Benefits

• Provides a robust and maintainable API server structure
• Enables efficient handling of HTTP requests
• Improves testability with Echo's built-in testing utilities
• Sets foundation for future API endpoint additions

Acceptance Criteria

• Echo framework is properly integrated with the application
• Configuration handling is implemented and tested
• GET endpoint successfully returns random Japanese phrases
• Unit tests are implemented with proper mock objects
• All tests pass successfully
• Documentation is updated with new API endpoints
• Performance metrics show acceptable response times