fix(teldrive): avoid index out of range panic when listing an empty dir

[SAY-5]

Summary / 摘要

When a Teldrive folder is empty the API returns totalPages: 0, so List sized pagesData to length 0 and then panicked on pagesData[0]. This made copying into an empty Teldrive directory (and listing one) crash with index out of range [0] with length 0. Returning early for the no-pages case fixes it; added a regression test that drives List against an empty-listing response.

• 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: N/A
• OpenList-Docs: N/A

Related Issues / 关联 Issue

Closes #2538

Testing / 测试

• go test ./...
• Manual test / 手动测试: go test ./drivers/teldrive/...; the new regression test hits the index out of range panic without the fix and passes with it.

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• I have read CONTRIBUTING.
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[jyxjjj]

Thank you for your contribution.

This pull request has been approved. However, before it can be merged, please update the PR description to match our default template. Do not remove any existing content; only reorganize or supplement it as needed to fit the template.

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[SAY-5]

Reorganized the description to follow the PR template, kept everything that was there.