feat(pdf): add DomPDF integration and ebook download feature

Integrate barryvdh/laravel-dompdf package for PDF generation with
custom configuration. Add authenticated ebook download route and view.
Update footer to display ebook download link for logged-in users.

bootstrap/providers.php

@@ -5,4 +5,5 @@ use App\Providers\AppServiceProvider;
 return [
     App\Providers\AppServiceProvider::class,
     App\Providers\AuthServiceProvider::class,
+    Barryvdh\DomPDF\ServiceProvider::class,
 ];