fix(ls): classify version listing backend failures as network

[overtrue]

Background

Recent changes tightened rc ls --versions behavior around missing buckets, but the adjacent generic backend-failure path was still untested.

Root Cause

S3Client::list_object_versions_page converted non-NotFound service failures into Error::General, and the ls --versions exit-code helper did not preserve Error::Network as a network exit code. That made retryable backend failures look like generic CLI failures.

Solution

Return Error::Network for non-missing-bucket list-version service failures and preserve that classification in rc ls --versions exit-code mapping.

Tests

• cargo test -p rc-s3 list_object_versions_page --lib
• cargo test -p rustfs-cli ls::tests --lib
• make pre-commit

[Copilot]

Pull request overview

This PR aligns rc ls --versions error classification with other listing paths by treating non-missing-bucket backend failures as retryable network errors and ensuring the CLI returns the corresponding network exit code.

Changes:

• Map non-NotFound/NoSuchBucket list_object_versions_page service failures to Error::Network.
• Preserve Error::Network as ExitCode::NetworkError in the ls --versions exit-code mapping.
• Add targeted unit tests in both the S3 client and CLI to cover the new behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
crates/s3/src/client.rs	Classifies non-missing-bucket list-version service failures as Error::Network and adds a regression test for 500/InternalError mapping.
crates/cli/src/commands/ls.rs	Maps Error::Network to ExitCode::NetworkError for version listing and adds a unit test for the mapping.

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