docs: add SQL practice template workflow

[GoZumie]

Summary

• Adds a Template Practice Repositories page with the git-basics- naming convention and proposed starter templates
• Reworks lessons 03-08 around a learner-owned git-basics-sql-practice repository
• Updates the practice checklist for SQL queries, data dictionaries, analysis notes, and PR feedback loops

Validation

• npm ci
• npm run build
• checked generated internal /git-basics content links