Add invoice PDF generation with dompdf

Install barryvdh/laravel-dompdf, create professional invoice Blade template
with EZSCALE branding, add download endpoints for customer billing and admin
invoice pages.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

website/app/Http/Controllers/Account/BillingController.php

@@ -7,6 +7,7 @@ namespace App\Http\Controllers\Account;
 use App\Http\Controllers\Controller;
 use App\Models\Invoice;
 use App\Services\Billing\BillingServiceFactory;
+use Barryvdh\DomPDF\Facade\Pdf;
 use Illuminate\Http\JsonResponse;
 use Illuminate\Http\RedirectResponse;
 use Illuminate\Http\Request;
@@ -93,13 +94,11 @@ class BillingController extends Controller
             abort(403);
         }
 
-        if ($invoice->invoice_pdf) {
-            return redirect($invoice->invoice_pdf);
-        }
+        $invoice->load(['user', 'items']);
 
-        // Generate a basic invoice download as JSON for now
-        // PDF generation will be added with a dedicated package
-        return response()->json($invoice->load('items'));
+        $pdf = Pdf::loadView('pdf.invoice', ['invoice' => $invoice]);
+
+        return $pdf->download("invoice-{$invoice->number}.pdf");
     }
 
     public function transactions(Request $request): Response