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)

.dockerignore

@@ -0,0 +1,44 @@
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+venv/
+env/
+ENV/
+.venv
+
+# Development
+.git/
+.gitignore
+*.md
+*.sh
+.vscode/
+.idea/
+
+# Database (will be created in volume)
+instance/*.db
+
+# Uploads (will be in volume)
+app/static/uploads/*
+static/uploads/*
+
+# Logs
+*.log
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Documentation
+BLUEPRINT_GUIDE.md
+ICON_INTEGRATION.md
+KIVY_PLAYER_COMPATIBILITY.md
+PLAYER_AUTH.md
+PROGRESS.md
+README.md
+
+# Config templates
+player_config_template.ini
+player_auth_module.py