feat: Release version 1.3.1 with Docker optimization and comprehensive documentation

- Update version to 1.3.1 in package.json and docker-compose.yml
- Optimize Dockerfile with proper data directory structure for production
- Add comprehensive Docker documentation (DOCKER.md)
- Include deployment and backup scripts (deploy.sh, backup.sh)
- Add .env.example for environment configuration
- Improve README with detailed deployment instructions
- Fix database path handling for Docker production environment
- Add health checks and proper Docker Compose configuration
- Remove development task documentation
- Update .gitignore to exclude backup directories

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.env.example

@@ -0,0 +1,8 @@
+# Variables de entorno para AP-POS
+# Copiar este archivo como .env y configurar los valores
+
+# Clave secreta para las sesiones (CAMBIAR en producción)
+SESSION_SECRET=tu-clave-secreta-muy-segura-cambiala-en-produccion
+
+# Entorno de ejecución
+NODE_ENV=production