Rails 8+ apps already include gem "pg", "~> 1.1" by default.
The template was unconditionally adding gem 'pg' causing a
Bundler error about duplicate gems with different versions.

Now checks if pg gem already exists before adding it.

Removed CSP module application from the template.

Co-authored-by: jaspermayone <65788728+jaspermayone@users.noreply.github.com>

Co-authored-by: jaspermayone <65788728+jaspermayone@users.noreply.github.com>

- Reorganize gems into logical categories with documentation
- Add Redis-backed session storage and caching
- Add Rack Attack for rate limiting and security throttling
- Add audit logging (audits1984, console1984)
- Add rails_performance monitoring
- Configure Redis cache store for production and development
- Create comprehensive admin dashboard with cards for all tools
- Fix typo: generare → generate