Update INSTALL.md for modern Python/Django setup

[qzMalekuz]

This PR updates INSTALL.md to reflect the current Python 3 and Django 4.2 setup.

Changes include:

• Updated Python version requirements
• Added virtual environment setup instructions
• Added migration and search index steps
• Clarified build/ directory requirement

[coleslaw481]

Nice, could you add notes about required packages. the old instructions had the user run pip install -r requirements.txt If you follow these steps from a clean environment can you run the unit tests?

[qzMalekuz]

Thanks! I added the dependency installation step (pip install -r requirements.txt) and instructions for running the unit tests.
I also verified the setup from a clean environment and the tests run successfully using make test.