feat: Add multi-worker support for uvicorn deployment

- Configure uvicorn to support multiple worker processes
- Add worker count configuration via environment variables
- Optimize Docker deployment for better resource utilization
- Enable horizontal scaling within single container instance

Improves application throughput and CPU utilization on multi-core systems.

src/mcpo/main.py

@@ -422,6 +422,7 @@ async def safe_lifespan(app: FastAPI):
             os.makedirs(worker_npx_cache, exist_ok=True)
 
             worker_env = {**env}
+            logger.info(f"worker_env after copy ({len(worker_env)} items):")
             worker_env.update({
                 "NPM_CONFIG_CACHE": worker_npm_cache,
                 "npm_config_cache": worker_npm_cache,