Consolidate PDF classes under app/Services/Pdf with consistent naming

Split PDFService.php (3 classes + 2 interfaces in one file) into separate
files. Move GotenbergPDFDriver from app/Services/PDFDrivers/ into
app/Services/Pdf/. Normalize casing from ALL-CAPS PDF to Pdf throughout:
facade, provider, service, driver factory, and Gotenberg driver.

Fix PaymentService using Barryvdh DomPDF facade directly instead of the
app's PDF facade (bypassed the driver factory). Report controllers also
updated to use the app facade.

app/Services/Pdf/PdfService.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace App\Services\Pdf;
+
+class PdfService
+{
+    public static function loadView(string $template)
+    {
+        $driver = config('pdf.driver');
+
+        return PdfDriverFactory::create($driver)->loadView($template);
+    }
+}