Fix harness PTY: bind to 0.0.0.0 instead of HOSTNAME

In K8s, HOSTNAME is set to the pod name, so the server only listened
on that interface. The PTY server's loopback fetch to 127.0.0.1 was
connection-refused. Always bind to 0.0.0.0 so loopback works.

apps/harness/server.js

@@ -3,7 +3,8 @@ const path = require("path");
 const { parse } = require("url");
 
 const dev = process.env.NODE_ENV !== "production";
-const hostname = process.env.HOSTNAME || "0.0.0.0";
+// HOSTNAME in K8s is the pod name — always bind to 0.0.0.0
+const hostname = "0.0.0.0";
 const port = parseInt(process.env.PORT || "3100", 10);
 
 // In production, load the standalone config to avoid webpack dependency