added patch and delete route for admin

[bernardev254]

Description

This PR introduces Update and Delete functionality for the Admin entity, following RESTful best practices and integrating seamlessly with the existing backend structure. Since Admins are represented as User records with the role: admin, these endpoints leverage the existing user service logic with additional role-based restrictions.

Summary of Changes

1. Added Update Admin Endpoint

• PATCH /admin/:id
• nAccepts partial admin data in the request body.
• Validates input before applying updates.
• Returns the updated admin object.

2. Added Delete Admin Endpoint

• DELETE /admin/:id
• Removes an admin record by ID.
• Returns confirmation of deletion (204 No Content).

3. Role-based Access Control

• Restricted access to these endpoints via RolesGuard.
• Only users with role: admin can perform these operations.

4. Controller & Module Updates

• Introduced AdminController under /admin.
• Integrated with UsersService for update and delete logic.

closes #195

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