feat(pdf-tools): add attachments feature to embed files in PDFs

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

docker-compose.yml

@@ -4,4 +4,4 @@ services:
     container_name: bentopdf
     restart: unless-stopped
     ports:
-      - "3000:80"
+      - '3000:80'