Upload failed after retry: check for duplicates first

A retry can be risky if the first upload actually completed but the confirmation failed. Before trying again, check the destination for a file with the same name or content. Record the time, file type, size range, last progress, and visible result of both attempts. Use a disposable file for diagnosis. If the service gives an upload ID, share it only if it is not a private token. A useful report states whether the retry resumed, restarted, created a duplicate, or failed during later processing, so cleanup does not accidentally remove the good copy.