Introduce PDF generation capabilities for shipments using laravel-dompdf.
This includes a new service layer, dedicated controller, and routes
to handle the generation of Air Waybills (AWB), Invoices, and Shipping
Labels.
- Add `PdfService` to encapsulate PDF generation logic.
- Add `ShipmentPdfController` to handle PDF download requests.
- Integrate `barryvdh/laravel-dompdf` dependency.
- Add Filament header actions to view shipment pages for quick PDF access.
- Update order success view to provide direct download links for documents.
- Add label methods to `ShipmentDirection` and `ShipmentType` enums.
- Update project status documentation to reflect initial PDF implementation.
