ColorlibHQ/gentelella ? reverse-engineered prompt

Build me a modern admin dashboard template for a SaaS or internal tool, using plain HTML, vanilla JavaScript, and SCSS, with a fast Vite build. It should feel polished and ready to demo, with a clean sidebar, responsive layouts, light and dark mode, and a PWA experience that can be installed and works well offline.

I want a good set of real admin pages too, like dashboards, login and register screens, inbox, kanban, calendar, file manager, charts, tables, forms, profile, settings, invoices, and a few error pages. Please include a theme editor where I can change the main color and see the whole UI update live, plus a component playground that shows reusable pieces and the exact HTML for them. Add a command palette for quick navigation, keyboard friendly interactions, and sensible accessibility throughout. Keep it framework free, no Bootstrap and no jQuery, and make it look production ready enough to use as a starting point for a real project.