FAQ, testimonial and rating presets, cleaner theme downloads

Downloaded themes install more cleanly in Ghost. FAQ, testimonial, and rating presets speed up new pages.

• Expanded preset and block library (FAQ, testimonials, ratings) for faster page setup.
• Added pagination and About sidebar block to Posts layouts.
• Normalized image URLs in theme ZIPs to reduce broken media after theme install.
• Improved migration and download dialogs for clearer project transfer and download flow.
• Fixed Ghost helper compatibility, including concat behavior.