refactor(policies): add uploadBackup ability and enforce it on backup upload endpoint

Introduce a dedicated `uploadBackup` ability on Application, Database,
Service, and ServiceDatabase policies (admin/owner only) and call
`$this->authorize('uploadBackup', $resource)` in `UploadController::upload`
so the backup-upload endpoint goes through the same policy layer as the
rest of the authorization refactor. Adds Pest coverage for each policy
variant plus HTTP-level checks.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/Http/Controllers/UploadController.php

@@ -2,6 +2,7 @@
 
 namespace App\Http\Controllers;
 
+use Illuminate\Foundation\Auth\Access\AuthorizesRequests;
 use Illuminate\Http\Request;
 use Illuminate\Http\UploadedFile;
 use Illuminate\Routing\Controller as BaseController;
@@ -11,6 +12,8 @@ use Pion\Laravel\ChunkUpload\Receiver\FileReceiver;
 
 class UploadController extends BaseController
 {
+    use AuthorizesRequests;
+
     public function upload(Request $request)
     {
         $databaseIdentifier = request()->route('databaseUuid');
@@ -18,6 +21,9 @@ class UploadController extends BaseController
         if (is_null($resource)) {
             return response()->json(['error' => 'You do not have permission for this database'], 500);
         }
+
+        $this->authorize('uploadBackup', $resource);
+
         $receiver = new FileReceiver('file', $request, HandlerFactory::classFromRequest($request));
 
         if ($receiver->isUploaded() === false) {