feat: allow copy config from existing configs

[Flartiny]

feat mentioned by #4020
允许从已存在的配置文件中复制，减少重复操作。
并且注意到此前是允许配置文件重名的，不利于辨识，故前端添加了校验（应该不影响已经创建的重名文件）。

Modifications / 改动点

dashboard/src/views/ConfigPage.vue
以及i18n（RU没能力做进一步校验了）

• 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

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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 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

Add ability to create new configs by copying existing ones and improve config name handling in the dashboard.

New Features:

• Allow users to copy an existing configuration to create a new one with its settings pre-filled.

Enhancements:

• Add validation to prevent duplicate or empty configuration names and update the config form title and save state accordingly.
• Expose copy, edit, and delete actions consistently in the config list UI and extend i18n strings for the new copy and validation messages.