fix: resolve PHPStan static analysis warnings

app/Http/Middleware/Admin.php

@@ -5,6 +5,7 @@ namespace App\Http\Middleware;
 use App\Exceptions\ApiException;
 use Illuminate\Support\Facades\Auth;
 use Closure;
+use App\Models\User;
 
 class Admin
 {
@@ -17,15 +18,13 @@ class Admin
      */
     public function handle($request, Closure $next)
     {
-        if (!Auth::guard('sanctum')->check()) {
-            throw new ApiException('未登录或登陆已过期', 403);
-        }
-
+        /** @var User|null $user */
         $user = Auth::guard('sanctum')->user();
-        if (!$user->is_admin) {
-            throw new ApiException('无管理员权限', 403);
+        
+        if (!$user || !$user->is_admin) {
+            return response()->json(['message' => 'Unauthorized'], 403);
         }
-
+        
         return $next($request);
     }
 }