feat: [dev] create dummy users

[rohan-chaturvedi]

🔍 Overview

Adds a management command to easily create dummy users and associate them with an org. This helps with development and testing code that requires multiple users to exist in an org.

🖼️ Screenshots or Demo

python manage.py create_dummy_users --count 1 --org "Starlink" --domain "example.com"
Created 1 dummy users and added them to 'Starlink'.

💚 Did You...

• Ensure linting passes (code style checks)?
• Update dependencies and lockfiles (if required)
  - [ ] Update migrations (if required)
  - [ ] Regenerate graphql schema and types (if required)
• Verify the app builds locally?
• Manually test the changes on different browsers/devices?