Replace type-specific document add/remove functions with generalized uploadDocuments and deleteDocument methods. Consolidate file upload handling in DocumentUploader for improved maintainability. Introduce evictCachedDocument to streamline cache eviction across document types. Update DocumentContext to support batch uploads and single-method deletion, simplifying context API and reducing duplication.
Remove temporary working directory usage and in-place file writes from preview
generation, simplifying logic for both PDF and EPUB previews. Change default
preview image variant from 480px to 400px width, updating related constants and
cache schema version to maintain consistency across client and server code.
Remove hardcoded defaults for preview variant and width in database schemas to allow more flexible preview generation. Bump preview cache schema version and add versioning to cache rows for consistency. Switch preview image generation to 480px JPEGs with updated file naming and content type. Refactor PDF preview rendering to support configurable output format and quality, and update all preview consumers to use unified "image" buffer property instead of "png". Add migration scripts and update metadata for both Postgres and SQLite.
BREAKING CHANGE: Preview variant and width defaults removed from database; preview cache and image handling updated across system.
