* Update CORSConfig to allow dynamic origins based on server instances.
* Add ExternalURLs field to ServerInstanceConfig for additional CORS support.
* Implement GetIPs function to retrieve non-local IP addresses for CORS.
- Add ServersConfig and ServerInstanceConfig structs
- Support configuring multiple named server instances
- Add global timeout defaults with per-instance overrides
- Add TLS configuration options (SSL cert/key, self-signed, AutoTLS)
- Add validation for server configurations
- Add helper methods for applying defaults and getting default server
- Add conversion helper to avoid import cycles