fix(s3): close ranged response bodies

[nostalume]

Summary / 摘要

Close the range body acquired by S3 GetObject before releasing its link. Previously Object.Contents.Close released only the link, leaving driver or HTTP range bodies open. The returned body now owns both resources through the existing multi-closer, preserving close errors and making repeated caller closes harmless.

The regression exercises the public backend boundary and verifies response bytes plus exact body-before-link close order. This does not change public API, configuration, storage format, lookup/cache behavior, metadata, range calculation, or S3 error mapping.

• This PR has breaking changes.
  / 此 PR 包含破坏性变更。
• This PR changes public API, config, storage format, or migration behavior.
  / 此 PR 修改了公开 API、配置、存储格式或迁移行为。
• This PR requires corresponding changes in related repositories.
  / 此 PR 需要关联仓库同步修改。

Related repository PRs / 关联仓库 PR:

• OpenList-Frontend: none
• OpenList-Docs: none

Testing / 测试

• go test ./... (not run; the complete affected package was tested)
• go test ./server/s3 -count=1 on Windows/amd64, Go 1.27.1
• go vet ./server/s3 on Windows/amd64, Go 1.27.1
• go test ./server/s3 -run '^TestGetObjectClosesRangeBodyBeforeLink$' -count=10 on Windows/amd64, Go 1.27.1
• CGO_ENABLED=1 go test -race ./server/s3 -run '^TestGetObjectClosesRangeBodyBeforeLink$' -count=3 on Linux/amd64 (tumbleweed WSL 2), Go 1.27.1

Checklist / 检查清单

• I have read CONTRIBUTING.
  / 我已阅读 CONTRIBUTING。
• I confirm this contribution follows the repository license, contribution policy, and code of conduct.
  / 我确认此贡献符合仓库许可证、贡献规范和行为准则。
• I have formatted the changed code with gofmt, go fmt, or prettier where applicable.
  / 已格式化变更代码。
• I have requested review from relevant maintainers or code owners where applicable. (Draft PR.)
  / 草稿 PR，尚未请求维护者审查。

AI Disclosure / AI 使用声明

• This PR includes AI-assisted content.
  / 此 PR 包含 AI 辅助内容。

Tools used / 使用工具:

• Codex

Usage scope / 使用范围:

• Code generation / 代码生成

• Tests / 测试

• Review assistance / 审查辅助

• I have reviewed and validated all AI-assisted content included in this PR.
  / 我已审核并验证此 PR 中的所有 AI 辅助内容。

• I have ensured that all AI-assisted commits include Co-Authored-By attribution.
  / 我已确保所有 AI 辅助提交都包含 Co-Authored-By 归属信息。

• I can reproduce all AI-assisted content included in this PR without any AI tools.
  / 我可以在没有任何 AI 工具的情况下重现此 PR 中包含的所有 AI 辅助内容。

[pikachuren]

🙏 感谢 @nostalume 提交！
🤖 AI 自动审核声明：本评审报告由 AI 自动生成，当前使用 Claude Opus 5 模型进行分析。
⚠️ AI 分析结果仅供参考，可能存在误判或遗漏。如您发现任何问题或有不同意见，欢迎随时提出讨论和纠正。
⚠️ 重要提醒：即使 AI 评审认为代码质量良好且建议合并，最终是否合并仍需由项目维护者进行人工判定。项目维护者会综合考虑代码质量、项目规划、技术方向、团队资源等多方面因素做出是否合并的决策。

🎯 结论

✅ Approve — 代码质量良好，建议合并

📖 概要

fix(s3): close ranged response bodies

📊 评审结果

改动合理，无重大问题发现。代码逻辑清晰，符合项目规范。

🎯 结论：✅ Approve — 建议合并