Limit-Status im Upload-Flow anzeigen (Warnbanner + Sperrzustände).

Upload-Fehlercodes auswerten und freundliche Dialoge zeigen.

app/Http/Controllers/OAuthController.php

@@ -7,6 +7,7 @@ use App\Models\OAuthCode;
 use App\Models\RefreshToken;
 use App\Models\Tenant;
 use App\Models\TenantToken;
+use App\Support\ApiError;
 use Firebase\JWT\JWT;
 use GuzzleHttp\Client;
 use Illuminate\Http\Request;
@@ -17,6 +18,7 @@ use Illuminate\Support\Facades\Hash;
 use Illuminate\Support\Facades\Log;
 use Illuminate\Support\Facades\Validator;
 use Illuminate\Support\Str;
+use Symfony\Component\HttpFoundation\Response;
 
 class OAuthController extends Controller
 {
@@ -690,7 +692,12 @@ class OAuthController extends Controller
     {
         $tenant = $request->user()->tenant ?? null;
         if (! $tenant) {
-            return response()->json(['error' => 'Tenant not found'], 404);
+            return ApiError::response(
+                'tenant_not_found',
+                'Tenant not found',
+                'The authenticated user is not assigned to a tenant.',
+                Response::HTTP_NOT_FOUND
+            );
         }
 
         $state = Str::random(40);