Don't crash Metro when the Rozenite panel port 8071 is already in use

[Mohamed-kassim]

Fixes #28.

With two Metro servers running at once (we run one per git worktree), the second one crashed on start because the Rozenite panel server always listens on 8071 and nothing handled the 'error' event from listen().

So runServer() now handles that event: on EADDRINUSE it prints a warning and Metro keeps running without its own panel server. Any other listen error gets a warning too, and a rejected createServer() no longer turns into an unhandled rejection.

[bundle-discovery] Port 8071 is already in use, probably by another Metro. The Bundle Discovery panel will show that server's bundle, not this one.

I tested the built plugin with 8071 held by a running Metro: it returned the config, printed the warning, and the process was still alive 8 seconds later. Before the change the same setup exited in about a second. yarn biome check, typecheck and build pass for the package, and there's a patch changeset.

The port itself stays hard-coded, because public/index.html points its iframe at http://localhost:8071. Making it configurable would mean telling the panel the port, which felt like a separate change. I put the port in a SERVER_PORT constant with a note about index.html so the two stay in sync.

[retyui]

thank you for PR , left small comment