fix: restore plugin view translations with legacy pages support

[wcqqq1214]

Fixes #10497.

Modifications / 改动点

• Restore plugin view titles/descriptions: prefer views.<name>, falling back to legacy pages.<name> per field.

• Translate flat/grouped sidebar view titles and refresh them on language changes.

• Update the English and Chinese guides. No API or navigation changes.

• This is NOT a breaking change. / 这不是一个破坏性变更。

Screenshots or Test Results / 运行截图或测试结果

• Switch Chinese/English with both views and legacy pages plugins: sidebar titles, context titles, and view content update correctly.
• Targeted checks passed for translation precedence, missing-field fallbacks, and grouped sidebar updates.
• Dashboard build/typecheck, docs build, Ruff format/check, and git diff --check passed. Both services rebuilt and restarted locally.

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Checklist / 检查清单

• 😊 If there are new features added in the PR, I have discussed it with the authors through issues/emails, etc.
  / 如果 PR 中有新加入的功能，已经通过 Issue / 邮件等方式和作者讨论过。

• 👀 My changes have been well-tested, and "Verification Steps" and "Screenshots" have been provided above.
  / 我的更改经过了良好的测试，并已在上方提供了“验证步骤”和“运行截图”。

• 📚 I checked the affected WebUI instructions and screenshots in docs/zh and docs/en against the changed navigation, page structure, and labels, and updated them in this PR (or explained why no documentation update is needed). For renamed, moved, or merged entry points, I included an old entry → new entry mapping in the documentation and changelog.
  / 我已对照变化后的 WebUI 入口、页面结构和术语，核对并在本 PR 中更新 docs/zh 和 docs/en 的相关操作说明与截图（或说明无需更新文档的原因）。入口改名、移动或合并时，已在文档和 changelog 中补充 旧入口 → 新入口 对照。

• 🤓 I have ensured that no new dependencies are introduced, OR if new dependencies are introduced, they have been added to the appropriate locations in requirements.txt and pyproject.toml.
  / 我确保没有引入新依赖库，或者引入了新依赖库的同时将其添加到 requirements.txt 和 pyproject.toml 文件相应位置。

• 😮 My changes do not introduce malicious code.
  / 我的更改没有引入恶意代码。

Summary by Sourcery

Restore plugin view translations while preserving support for legacy page translation keys.

Bug Fixes:

• Restore localized plugin view titles in the sidebar and plugin pages, including compatibility with legacy pages.<view_name> translations.

Enhancements:

• Refresh flat and grouped plugin sidebar titles when the WebUI language changes, with per-field translation fallback from views.<view_name> to pages.<view_name>.

Documentation:

• Document localized sidebar titles and the legacy translation-key fallback in the English and Chinese plugin view guides.

[sourcery-ai]

Hey - I've reviewed your changes and they look great!

Sourcery assessment

Approved.

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[Soulter]

感谢 PR！#10502 已经做了类似修复。