refactor: migrate to Elysia and enhance security middleware

- Replaced Express with Elysia for improved performance and type safety
- Integrated Elysia middleware for rate limiting, security headers, and request validation
- Refactored security utilities to work with Elysia's context and request handling
- Updated token management and validation logic
- Added comprehensive security headers and input sanitization
- Simplified server initialization and error handling
- Updated documentation with new setup and configuration details

docs/development/README.md

@@ -7,6 +7,8 @@ This guide provides information for developers who want to contribute to or exte
 ```
 homeassistant-mcp/
 ├── src/
+│   ├── __tests__/        # Test files
+│   ├── __mocks__/       # Mock files
 │   ├── api/           # API endpoints and route handlers
 │   ├── config/        # Configuration management
 │   ├── hass/         # Home Assistant integration