Rendering engine v2 and style picker
Added the second rendering engine, design-system foundations, Blade templates, iframe previews, ULID identifiers, custom CSS support, and a style picker.
What changed
- Added design-system-aware rendering with iframe previews.
- Moved pages, versions, and sites to ULID identifiers.
- Added custom CSS and expanded section support.
- Added a style picker so customers can choose a visual direction.
Why it matters
This release gave early generated sites a stronger rendering foundation and introduced the first customer-facing style selection workflow.