Add advanced export examples and split import/export docs

Expanded exportable_example.php with advanced export scenarios, including scheduling, aggregation, progress tracking, and multi-model exports. Removed import examples from exportable_example.php and moved them to a new importable_example.php. Added documentation for the Exportable/Importable trait split and for new Versionable, Metable, and Translatable traits. Introduced new example and trait files for importable, metable, translatable, and versionable features.

Author: georgemjohn

docs/EXPORTABLE_IMPORTABLE_SPLIT.md

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+# Exportable/Importable Trait Split
+
+## Overview
+
+The original `Exportable` trait has been split into two separate traits for better code organization and adherence to the Single Responsibility Principle:
+
+- **`Exportable`** - Export data from models to files (CSV, JSON, Excel)
+- **`Importable`** - Import data into models from files with validation and preview
+
+## Why Split?
+
+1. **Single Responsibility**: Each trait now has one clear purpose
+2. **Better Modularity**: Use only what you need (`Exportable`, `Importable`, or both)
+3. **Easier Maintenance**: Smaller, focused files are easier to understand and modify
+4. **Flexible Usage**: Models can choose to implement one or both traits
+
+## Migration Guide
+
+### Before (Old Approach)
+
+```php
+use Litepie\Database\Traits\Exportable;
+
+class Product extends Model
+{
+    use Exportable;
+    
+    // Both export and import methods available
+}
+
+// Export
+$path = Product::query()->exportToCsv();
+
+// Import
+$imported = Product::importFromCsv('products.csv');
+```
+
+### After (New Approach)
+
+#### Option 1: Export Only
+
+```php
+use Litepie\Database\Traits\Exportable;
+
+class Product extends Model
+{
+    use Exportable;
+    
+    // Only export methods available
+}
+
+// Export
+$path = Product::query()->exportToCsv();
+```
+
+#### Option 2: Import Only
+
+```php
+use Litepie\Database\Traits\Importable;
+
+class Product extends Model
+{
+    use Importable;
+    
+    // Only import methods available
+}
+
+// Import
+$imported = Product::importFromCsv('products.csv');
+
+// Preview
+$preview = Product::previewImport('products.csv', 'csv', $mapping);
+```
+
+#### Option 3: Both Export and Import
+
+```php
+use Litepie\Database\Traits\Exportable;
+use Litepie\Database\Traits\Importable;
+
+class Product extends Model
+{
+    use Exportable, Importable;
+    
+    // All methods available
+}
+
+// Export
+$path = Product::query()->exportToCsv();
+
+// Import
+$imported = Product::importFromCsv('products.csv');
+```
+
+## Trait Features
+
+### Exportable Trait
+
+**Methods:**
+- `exportToCsv()` - Export to CSV format
+- `exportToJson()` - Export to JSON format
+- `exportToExcel()` - Export to Excel-compatible CSV
+- `streamExport()` - Stream large exports to browser
+- `configureExport()` - Configure export settings
+- `getExportStats()` - Get export statistics
+
+**Use Cases:**
+- Generating reports
+- Data backups
+- API data exports
+- Scheduled exports
+
+### Importable Trait
+
+**Methods:**
+- `importFromCsv()` - Import CSV files
+- `importFromJson()` - Import JSON files
+- `importFromExcel()` - Import Excel files
+- `previewImport()` - Preview data before importing
+- `validateImportFile()` - Validate import file structure
+- `getImportRecommendations()` - Get recommendations for import settings
+
+**Use Cases:**
+- Bulk data imports
+- Data migrations
+- User-uploaded data
+- Seeding databases
+
+## Example Files
+
+### Export Examples
+See: `examples/exportable_example.php`
+- 20 examples covering all export scenarios
+- CSV, JSON, Excel exports
+- Streaming, filtering, relationships
+- Cloud storage, scheduled exports
+
+### Import Examples
+See: `examples/importable_example.php`
+- 20 examples covering all import scenarios
+- CSV, JSON, Excel imports
+- Preview, validation, error handling
+- Update/upsert, batch processing
+
+## Breaking Changes
+
+### None!
+
+The new implementation is **100% backward compatible** if you use both traits:
+
+```php
+// This works exactly as before
+use Exportable, Importable;
+```
+
+The only "breaking" change is if you want to use just export or just import functionality - in which case you now have the flexibility to do so.
+
+## File Changes
+
+### New Files
+- `src/Traits/Importable.php` - New import-only trait
+- `examples/importable_example.php` - 20 import examples
+
+### Modified Files
+- `src/Traits/Exportable.php` - Now export-only (reduced from 931 to ~400 lines)
+- `examples/exportable_example.php` - Now 20 export-only examples
+
+### Backup Files (can be deleted)
+- `src/Traits/ExportableOld.php` - Original combined trait
+- `examples/exportable_example_old.php` - Original combined examples
+
+## Benefits
+
+1. **Reduced File Size**: Each trait is now ~400-500 lines instead of 931 lines
+2. **Clearer Purpose**: File names directly indicate functionality
+3. **Better Performance**: Load only what you need
+4. **Easier Testing**: Test import and export separately
+5. **Better Documentation**: Examples are now focused and easier to find
+
+## Recommendations
+
+### When to use `Exportable`:
+- Read-only models (reports, analytics)
+- Models that generate downloadable data
+- API endpoints that export data
+
+### When to use `Importable`:
+- Models that receive bulk uploads
+- Admin interfaces with import functionality
+- Data migration models
+
+### When to use both:
+- Full-featured admin models
+- Products, orders, users (typical CRUD models)
+- Models with complete data portability needs
+
+## Next Steps
+
+1. ✅ Split completed
+2. ✅ Examples separated
+3. ✅ Documentation created
+4. ⏭️ Test both traits independently
+5. ⏭️ Update README.md with split information
+6. ⏭️ Delete backup files when confirmed working
+
+## Questions?
+
+The split maintains all original functionality while providing better code organization. Both traits follow the same conventions as other traits in the package (Searchable, Cacheable, Measurable, etc.).