fix(docker): include apps/shared in dashboard image build

The shared websocket package is a web file: dependency but was excluded
by .dockerignore and never copied into the Docker build context. Also fix
tsc -b errors: expose buildWsUrl on api and drop the GatewayClient state
getter that conflicted with the shared base class.

web/src/lib/api.ts

@@ -315,6 +315,7 @@ function appendProfileParam(url: string, profile?: string): string {
 }
 
 export const api = {
+  buildWsUrl,
   getStatus: () => fetchJSON<StatusResponse>("/api/status"),
   /**
    * Identity probe for the dashboard auth gate (Phase 7).