Add ZIP-based user data download endpoint, enable AES-256 server-side S3 encryption for all stored documents and audiobooks. Rewrite privacy policy with detailed CCPA categories, service provider disclosures (Vercel/Neon/Railway), and user rights sections. Replace privacy modal with checkbox agreement flow.
- Add document preview caching logic with in-memory and persisted storage.
- Implement S3 blobstore functions for managing document previews.
- Create rendering functions for PDF and EPUB cover images to JPEG format.
- Introduce database schema and functions for managing document preview metadata.
- Add unit tests for rendering PDF and EPUB previews.