feat: add SSR plugin and tests for server-side rendering capabilities
- Implemented ssrPlugin for Fastify to enable server-side rendering with Vite.
- Created tests for ssrPlugin to ensure proper registration and functionality.
- Added SsrRouter and SsrService with corresponding tests for routing and rendering.
- Included TypeScript configuration and build setup for SSR package.
- Documented SSR usage and configuration in the website documentation.