Rename controller namespaces: drop V1 prefix, clarify roles

V1/Admin     -> Company       (company-scoped controllers)
V1/SuperAdmin -> Admin        (platform-wide admin controllers)
V1/Customer  -> CustomerPortal (customer-facing portal)
V1/Installation -> Setup      (installation wizard)
V1/PDF       -> Pdf           (consistent casing)
V1/Modules   -> Modules       (drop V1 prefix)
V1/Webhook   -> Webhook       (drop V1 prefix)

The V1 prefix served no purpose - API versioning is in the route prefix
(/api/v1/), not the controller namespace. "Admin" was misleading for
company-scoped controllers. "SuperAdmin" is now simply "Admin" for
platform administration.

app/Http/Controllers/Pdf/DownloadInvoicePdfController.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace App\Http\Controllers\Pdf;
+
+use App\Http\Controllers\Controller;
+use App\Models\Invoice;
+use Illuminate\Http\Request;
+use Illuminate\Http\Response;
+
+class DownloadInvoicePdfController extends Controller
+{
+    /**
+     * Handle the incoming request.
+     *
+     * @param  Request  $request
+     * @return Response
+     */
+    public function __invoke(Invoice $invoice)
+    {
+        $path = storage_path('app/temp/invoice/'.$invoice->id.'.pdf');
+
+        return response()->download($path);
+    }
+}