fix(aliyundrive): limit callback concurrency

[nostalume]

Summary / 摘要

• Add a per-Aliyun-user admission limit for proxied callback downloads. The new Callback Concurrency storage setting defaults to 1; nonpositive legacy values normalize to 1, and mounts sharing a user use the smallest live limit.

• Hold admission for the complete response-body lifetime and release it exactly once on EOF, read failure, cancellation, or Close. Direct 302 links remain URL-only and proxy readers retain the server download limiter.

• Retry only HTTP 403 callback responses containing both RequestDeniedByCallback and ExceedMaxConcurrency, with three total attempts and bounded exponential jitter.

• Return a typed temporary-capacity error after bounded admission/retry exhaustion and translate only that error to standard S3 SlowDown / HTTP 503.

• Advance the official github.com/OpenListTeam/gofakes3 dependency from v0.8.1 to merged commit cd3c030a83b4, which provides the required SlowDown error.

• 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: Not required; storage fields are metadata-driven.
• OpenList-Docs: docs(aliyundrive): explain callback concurrency OpenList-Docs#370

Related Issues / 关联 Issue

Relates to #2969

Testing / 测试

Validated after rebasing onto OpenList main at f18b4ac with Go 1.27.1:

• go test ./drivers/aliyundrive_open -count=5
• Relevant S3 error, range, and redirect tests with -count=5
• go test ./server/s3 -run '^$'
• go test -vet=off ./... -run '^$'
• go vet ./drivers/aliyundrive_open ./server/s3
• go mod verify
• go test ./server/s3 -count=1
  • The new and related tests pass. The Windows package run reaches four upstream multipart tests that reject manually interpolated temporary paths as invalid JSON escapes; the independent test-only repair is fix(s3): encode multipart fixture paths #3074. The complete package passes under Linux race instrumentation below.
• go test -race ./drivers/aliyundrive_open -count=1 (Go 1.27.1, Tumbleweed WSL, CGO enabled, GCC 16.2.0)
• go test -race ./server/s3 -count=1 (same environment; complete package including multipart tests)
• Manual test / 手动测试:
  • No live Aliyun account canary was run. Deterministic transports cover peak active bodies, same-user sharing, independent users, reconfiguration drain, cancellation, all body release paths, exact provider-error classification, URL redaction, and S3 503/XML output.

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.
  / 我已按适用情况使用 gofmt、go fmt 或 prettier 格式化变更代码。
• I have requested review from relevant maintainers or code owners where applicable.
  / 我已在适用情况下请求相关维护者或代码所有者审查。

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:

• ChatGPT
• Codex
• GitHub Copilot
• Claude
• Gemini
• Other (please specify) / 其他（请注明）:

Usage scope / 使用范围:

• Code generation / 代码生成

• Refactoring / 重构

• Documentation / 文档

• Tests / 测试

• Translation / 翻译

• 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。

This draft intentionally leaves the human-review and reproducibility confirmations unchecked for the author to complete after review.