[FEAT]: Add run instructions to frontend/README.md

[openrxcreator]

Goal
Add a short section to frontend/README.md showing how to run the frontend locally.

Steps

1. Open frontend/README.md
2. Add run commands such as:
   npm install
   npm start
3. Keep the instructions short (2–4 lines)

Acceptance criteria

• frontend/README.md includes simple, clear run instructions
• Commands are copy-paste friendly

[Mustansir-06]

Please assign this to me. Thanks!