GitLab

* Add preflight OPTIONS handling and update CORS config

- Implement early return with HTTP 204 (No Content) for OPTIONS requests in allowedHostsMiddleware to optimize preflight handling.

- Extend CORS configuration to explicitly allow 'Authorization' headers and 'OPTIONS' method when OLLAMA_ORIGINS environment variable is set.

* allow auth, content-type, and user-agent headers

* Update routes.go