fix: file storage module should abort file download on request cancellation

[Roshan931]

Fixes #1248

Root cause

S3 file download ignores request context cancellation

Changes

• Use s3manager Downloader.DownloadWithContext with the request-scoped context in AmazonS3.ReadFile so the download aborts when the HTTP request is cancelled; the existing error path already closes and removes the temp file.

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