Enable early hints in Control Plane production deployment

Added --early-hints flag to the Rails server command in the Control
Plane Dockerfile. This enables Puma to send HTTP 103 Early Hints
responses in production, allowing browsers to preload assets while
the server is still preparing the HTML response.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

.controlplane/Dockerfile

@@ -79,4 +79,4 @@ ENTRYPOINT ["./.controlplane/entrypoint.sh"]
 
 # Default args to pass to the entry point that can be overridden
 # For Kubernetes and ControlPlane, these are the "workload args"
-CMD ["./bin/rails", "server"]
+CMD ["./bin/rails", "server", "--early-hints"]