Expand README with actionable setup and validation docs

[Copilot]

The repository’s documentation was effectively empty, which left contributors without a clear path to run the app locally. This change replaces the placeholder README with concise, executable project documentation.

• What changed

  • Replaced the one-line README with a structured guide for:
    • project purpose
    • runtime prerequisites
    • local environment setup
    • database migration
    • development server startup
    • built-in project validation commands

• Developer workflow now documented

  • Standardized command examples for day-1 usage:

  pip install -r requirements.txt
  python manage.py migrate
  python manage.py runserver
  python manage.py test
  python manage.py check