Populate SQL Server Test Database with Realistic Sample Data

[c-wilkinson]

Enhance the PowerShell script to populate the TestLab database with realistic sample data.
The goal is to make the environment reusable and immediately useful for testing and demos. So far, it just contains the schema setup.

Sample data should include:

• Number of users, products, and orders based on the existing parameters.
• Consistent relationships between tables (e.g. valid foreign keys, order totals that match order items).
• Meaningful content in text fields (e.g. usernames, product names, categories, post titles).

This will make the database a fully self-contained, redeployable test system that can be recreated on demand for development or demonstration purposes.