docs(contributing): fix studio dev server port in setup guide (#2901)

- Problem: setup guide pointed contributors to localhost:3000 after bun run dev.
- Fix: use localhost:5190 to match packages/studio/vite.config.ts server.port.
- Verification: preflight_ship.py + read vite.config.ts server.port (5190).

Author: santhiprakash

docs/contributing.mdx

@@ -32,7 +32,7 @@ Thanks for your interest in contributing to Hyperframes! This guide covers every
     ```bash
     bun run dev
     ```
-    If the studio opens at `http://localhost:3000` with a preview, your environment is ready.
+    If the studio opens at `http://localhost:5190` with a preview, your environment is ready.
   </Step>
   <Step title="Create a branch">
     Create a feature branch for your work: