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/Admin/Update/CheckVersionController.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace App\Http\Controllers\Admin\Update;
+
+use App\Http\Controllers\Controller;
+use App\Services\Update\Updater;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\File;
+
+class CheckVersionController extends Controller
+{
+    /**
+     * Handle the incoming request.
+     *
+     * @return JsonResponse
+     */
+    public function __invoke(Request $request)
+    {
+        if ((! $request->user()) || (! $request->user()->isOwner())) {
+            return response()->json([
+                'success' => false,
+                'message' => 'You are not allowed to update this app.',
+            ], 401);
+        }
+
+        set_time_limit(600); // 10 minutes
+
+        $channel = $request->get('channel', 'stable');
+        $version = preg_replace('~[\r\n]+~', '', File::get(base_path('version.md')));
+        $response = Updater::checkForUpdate($version, $channel);
+
+        return response()->json($response);
+    }
+}