Added doctor assignment management page by Shubham Rana

[SHUBHAM-2305]

Description

Implemented Task 7: Doctor Assignment Management for the admin dashboard.

This PR adds a new Doctor Assignments module where admins can view doctors, see assigned patients, and manage doctor-patient assignments from one separate page. Since the actual backend is not connected yet, mock doctor and patient data has been added to test the frontend flow locally.

Todos

• Tested and working locally
• Code follows the style guidelines of this project
• I have performed a self-review of my code
• Code changes documented
• Requested review from >= 2 devs on the team (one frontend and one backend recommended)

How to test

1. Pull this branch and run the admin dashboard locally.

npm install
npm run dev 

##GUI
<img width="800" height="412" alt="a51d0621-9084-4a7a-8be2-bf30638ca8ed" src="https://github.com/user-attachments/assets/abbd6523-31de-4513-ad8a-ab1ebf2514ee" />