* fix: enhance app icon download logic to include file existence check
- Updated the downloadAppIcon function to parse the icon field for the file name and ETag.
- Added a condition to check if the icon file exists before setting the If-None-Match header for the request.
* fix: improve app icon retrieval logic by adding filename check
- Updated GetAppIcon method to include filename in the response.
- Added a condition to ensure the ETag header is set only if both ETag and filename are present, enhancing the integrity of the caching mechanism.