Change onSuccess to onSettled for upload mutations so the file tree
refreshes regardless of success or failure, ensuring consistency when
backend creates nodes but storage upload fails.
Previously, media files were fetched via getFileContent API which decodes
binary data as UTF-8, resulting in corrupted strings that cannot be used
as img/video src. Now media files use getFileDownloadUrl API to get a
presigned URL, enabling proper preview of images and videos of any size.
When file content is not in JSON format (e.g., newly uploaded files),
return the raw content instead of empty string to ensure files display
correctly.
Extract repeated appId retrieval and tree data fetching patterns into
dedicated hooks (useSkillAssetTreeData, useSkillAssetNodeMap) to reduce
code duplication across 6 components and leverage TanStack Query's
select option for efficient nodeMap computation.
