Implement new functionality to allow embedding attachments into PDF documents. The feature includes:
- UI for selecting PDF and files to attach
- Logic to embed files while preserving metadata
- Display of attached files with size information
- Download of modified PDF with embedded files
Add development docker-compose configuration and switch production config to use pre-built image
docs: update README with improved setup instructions and new features
refactor: convert script tags to link tags for stylesheets in HTML files
fix: update PDF download to use Uint8Array for blob creation
style: reformat CSS file for better readability and organization