Add Docker support and improve PDF conversion

Features:
- Dockerfile for containerized deployment
- Docker Compose configuration with health checks
- Automated database initialization via entrypoint script
- Quick start script for easy Docker deployment
- Comprehensive Docker deployment documentation (DOCKER.md)
- Complete README with installation and usage instructions
- .dockerignore for optimized image builds

Improvements:
- PDF conversion now preserves orientation (portrait/landscape)
- PDF rendering at 300 DPI for sharp quality
- Maintains aspect ratio during conversion
- Compact media library view with image thumbnails
- Better media preview with scrollable gallery

Docker Features:
- Multi-stage build for smaller images
- Non-root user for security
- Health checks for container monitoring
- Volume mounts for persistent data
- Production-ready Gunicorn configuration
- Support for Redis caching (optional)

DOCKER.md

@@ -0,0 +1,252 @@
+# Docker Deployment Guide
+
+## Quick Start
+
+### 1. Build and Run with Docker Compose
+
+```bash
+# Build the Docker image
+docker-compose build
+
+# Start the container
+docker-compose up -d
+
+# View logs
+docker-compose logs -f
+
+# Stop the container
+docker-compose down
+```
+
+The application will be available at `http://localhost:5000`
+
+Default credentials:
+- Username: `admin`
+- Password: `admin123`
+
+### 2. Build Docker Image Only
+
+```bash
+# Build the image
+docker build -t digiserver-v2:latest .
+
+# Run the container
+docker run -d \
+  -p 5000:5000 \
+  -v $(pwd)/instance:/app/instance \
+  -v $(pwd)/app/static/uploads:/app/app/static/uploads \
+  --name digiserver \
+  digiserver-v2:latest
+```
+
+## Configuration
+
+### Environment Variables
+
+Create a `.env` file based on `.env.example`:
+
+```bash
+cp .env.example .env
+```
+
+Edit the `.env` file to set your configuration:
+- `SECRET_KEY`: Change to a random secret key
+- `FLASK_ENV`: Set to `production` for production deployments
+
+### Persistent Data
+
+The following directories are mounted as volumes:
+- `./instance`: Database storage
+- `./app/static/uploads`: Uploaded media files
+
+These persist even when containers are recreated.
+
+## Production Deployment
+
+### 1. Using Docker Compose (Recommended)
+
+```bash
+# Create .env file with production settings
+cp .env.example .env
+nano .env  # Edit with your settings
+
+# Start in production mode
+docker-compose up -d
+```
+
+### 2. Behind a Reverse Proxy (Nginx/Traefik)
+
+Example Nginx configuration:
+
+```nginx
+server {
+    listen 80;
+    server_name yourdomain.com;
+
+    location / {
+        proxy_pass http://localhost:5000;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        
+        # For large file uploads
+        client_max_body_size 100M;
+    }
+}
+```
+
+### 3. Enable Redis Caching (Optional)
+
+Uncomment the Redis service in `docker-compose.yml`:
+
+```yaml
+  redis:
+    image: redis:7-alpine
+    container_name: digiserver-redis
+    restart: unless-stopped
+    volumes:
+      - redis-data:/data
+
+volumes:
+  redis-data:
+```
+
+Update `.env`:
+```
+REDIS_URL=redis://redis:6379/0
+```
+
+## Backup
+
+### Database Backup
+
+```bash
+# Backup database
+docker exec digiserver tar -czf /tmp/backup.tar.gz /app/instance
+docker cp digiserver:/tmp/backup.tar.gz ./backup-$(date +%Y%m%d).tar.gz
+```
+
+### Full Backup (Database + Uploads)
+
+```bash
+# Backup everything
+tar -czf digiserver-backup-$(date +%Y%m%d).tar.gz instance/ app/static/uploads/
+```
+
+## Maintenance
+
+### View Logs
+
+```bash
+# All logs
+docker-compose logs -f
+
+# Last 100 lines
+docker-compose logs --tail=100
+
+# Specific service
+docker-compose logs -f digiserver
+```
+
+### Update Application
+
+```bash
+# Pull latest code
+git pull
+
+# Rebuild and restart
+docker-compose down
+docker-compose build
+docker-compose up -d
+```
+
+### Shell Access
+
+```bash
+# Access container shell
+docker-compose exec digiserver bash
+
+# Or with docker directly
+docker exec -it digiserver bash
+```
+
+## Troubleshooting
+
+### Port Already in Use
+
+Change the port mapping in `docker-compose.yml`:
+```yaml
+ports:
+  - "8080:5000"  # Change 8080 to your desired port
+```
+
+### Permission Issues
+
+Ensure the volumes have correct permissions:
+```bash
+sudo chown -R 1000:1000 instance/ app/static/uploads/
+```
+
+### Container Won't Start
+
+Check logs:
+```bash
+docker-compose logs digiserver
+```
+
+### Reset Database
+
+```bash
+# Stop containers
+docker-compose down
+
+# Remove database
+rm instance/*.db
+
+# Start fresh
+docker-compose up -d
+```
+
+## System Requirements
+
+- Docker 20.10+
+- Docker Compose 2.0+
+- 2GB RAM minimum
+- 10GB disk space for media files
+
+## Security Recommendations
+
+1. **Change default credentials** immediately after first login
+2. **Set a strong SECRET_KEY** in `.env`
+3. **Use HTTPS** with a reverse proxy in production
+4. **Regular backups** of database and uploads
+5. **Update regularly** to get security patches
+6. **Restrict network access** using firewall rules
+7. **Monitor logs** for suspicious activity
+
+## Performance Tuning
+
+### Adjust Workers
+
+Edit `Dockerfile` CMD line:
+```dockerfile
+CMD ["gunicorn", "--bind", "0.0.0.0:5000", "--workers", "8", "--timeout", "120", "app.app:create_app()"]
+```
+
+### Resource Limits
+
+Add to `docker-compose.yml`:
+```yaml
+services:
+  digiserver:
+    # ... existing config ...
+    deploy:
+      resources:
+        limits:
+          cpus: '2'
+          memory: 2G
+        reservations:
+          cpus: '1'
+          memory: 1G
+```