Cloudflare R2 backup - Improved buffer handling

[patrickvorgers]

Proposed change

The new IDrive-e2 S3 backup implementation introduces improved buffer handling using memoryview.
During the review of #144910, it was requested to apply the same approach to the other S3-compatible backup implementations.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: N/A
• This PR is related to issue: Follow-up to IDrive e2 backup provider #144910 (request during review/merge to apply the same buffer handling to other S3-compatible backup implementations)
• Link to documentation pull request: N/A
• Link to developer documentation pull request: N/A
• Link to frontend pull request: N/A

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[home-assistant]

Hey there @corrreia, mind taking a look at this pull request as it has been labeled with an integration (cloudflare_r2) you are listed as a code owner for? Thanks!

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[Copilot]

Pull request overview

This PR applies improved buffer handling from the IDrive e2 backup implementation (#144910) to the Cloudflare R2 backup integration. The changes introduce memoryview-based buffer management with offset tracking to reduce memory copies during multipart uploads, improving performance for large backup files.

Changes:

• Added memoryview-based buffer handling with offset tracking for multipart uploads
• Implemented buffer compaction logic to avoid unnecessary memory copies
• Added cast(Any, ...) for client method calls to handle type checking

[corrreia]

This looks good! A a solid improvement, especially for bigger backup sizes

[corrreia]

Have you tested this with multipart uploads? R2 can be pretty finicky with those in my experience

[patrickvorgers]

Have you tested this with multipart uploads? R2 can be pretty finicky with those in my experience

I tested it against idrive-e2 because I don't have Cloudflare-R2. Would be great if you could verify,
I didn't change anything in the different multipart sizes but it is good to double check.

[zweckj]

LGTM, can be merged as soon as @corrreia confirms multi part

[corrreia]

@zweckj confirmed, multipart works!