Fix file extension validation to use original filename

The file extension validation was checking the temporary file path
which doesn't have an extension. This fix changes it to check the
original filename's extension instead, allowing proper validation
of uploaded files.

src/FS/File.php

@@ -506,7 +506,7 @@ public static function upload($file, string $destination, array $options = [])
 
         if ($options['validate']) {
             $fileType = static::type($temp);
-            $fileExtension = (new Path($temp))->extension();
+            $fileExtension = (new Path($file['name']))->extension();  // Changed from $temp to $file['name'] to fix extension validation
 
             if (
                 !empty($options['allowedTypes']) &&