Adds server.forward-headers-strategy: native so that Jetty honours
X-Forwarded-{Proto,For,Host} from Caddy. Without this, getScheme(),
redirect URLs, and Spring Session "Secure" cookies reflect the
internal http hop instead of the original https client request.
Refs #497.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>