feat: optional NPM proxy per stage

Add enable_proxy boolean to stages (default true). When disabled,
the deployer skips NPM proxy host creation — useful for internal
services, workers, or externally-routed containers. UI shows
toggle in Add Stage form and "No Proxy" badge on stage header.

web/src/lib/types.ts

@@ -21,6 +21,7 @@ export interface Stage {
 	auto_deploy: boolean;
 	max_instances: number;
 	confirm: boolean;
+	enable_proxy: boolean;
 	promote_from: string;
 	subdomain: string;
 	created_at: string;