Crypto Porto

This build includes improvements to the local data export and import functionality. What changed: - Users can now select which portfolio they want to export before generating an export file. - Export is available in both CSV and JSON formats. - Exported files now include clearer portfolio metadata, including the portfolio name and export date. - Import handling has been improved for both CSV and JSON files. - The app now validates imported files before applying changes. - Users receive a preview/confirmation before importing portfolio data. - Existing portfolio name conflicts are handled more safely. - Invalid or unsupported files now show a clear error message instead of causing issues. The feature has been tested successfully with: - JSON export and re-import - CSV export and re-import - Portfolio selection before export - Import validation and confirmation flow All user data remains stored locally on the device. No account or external server is required.