Feat: add export functionality with GUI for data and graphs

- Implemented ExportWindow class for exporting data and graphs in various formats (JSON, XML, PDF).
- Integrated ExportManager to handle export logic.
- Added export option in the main application menu.
- Enhanced user interface with data summary and export options.
- Included error handling and success messages for export operations.
- Updated dependencies in the lock file to include reportlab and lxml for PDF generation.

README.md

@@ -15,6 +15,7 @@ make test
 
 ## 📚 Documentation
 - **[Features Guide](docs/FEATURES.md)** - Complete feature documentation
+- **[Export System](docs/EXPORT_SYSTEM.md)** - Data export functionality and formats
 - **[Development Guide](docs/DEVELOPMENT.md)** - Testing, development, and architecture
 - **[Changelog](docs/CHANGELOG.md)** - Version history and feature evolution
 - **[Quick Reference](#quick-reference)** - Common commands and shortcuts
@@ -226,6 +227,13 @@ On first run, the application will:
 - **Backward Compatibility**: Seamless upgrades without data loss
 - **Dynamic Columns**: Adapts to new medicines and pathologies
 
+### 📋 Data Export System
+- **Multiple Formats**: Export to JSON, XML, and PDF formats
+- **Comprehensive Reports**: PDF exports with optional graph visualization
+- **Metadata Inclusion**: Export includes date ranges, pathologies, and medicines
+- **User-Friendly Interface**: Easy access through File menu with format selection
+- **Data Portability**: Structured exports for analysis or backup purposes
+
 For complete feature documentation, see **[docs/FEATURES.md](docs/FEATURES.md)**.
 
 ## Development