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.
This commit restructures the audiobook generation and serving layer to rely exclusively on S3-compatible blob storage, removing the dependency on local filesystem paths.
- Bundle `ffmpeg` and `ffprobe` binaries via npm to ensure portability across environments.
- Update API routes to stream audio directly from blob storage instead of local disk.
- Remove legacy migration endpoints and filesystem-based indexing logic.
- Add startup scripts to facilitate the transition from local to remote storage.
BREAKING CHANGE: Audiobook functionality is now strictly dependent on S3 configuration. The previous filesystem-based storage method has been removed.
