[Sunrisea]

Related #14807

What is the purpose of the change

When a prompt is deleted through the new lifecycle governance API, the legacy latest mirror config ({promptKey}.json in nacos-ai-prompt group) is not cleaned up. This leaves orphan configs in the legacy storage location.

Brief changelog

• Add deleteLegacyLatestMirror to the deletePrompt flow in PromptOperationServiceImpl
• Delete {promptKey}.json from nacos-ai-prompt group when a prompt is removed
• Failure to delete the legacy mirror is caught and logged as a warning, does not block the main deletion

Verifying this change

This change includes unit tests:

• testDeletePromptShouldCleanLegacyLatestMirror — verifies configOperationService.deleteConfig is called with the correct dataId/group
• testDeletePromptShouldNotFailWhenLegacyMirrorDeleteThrows — verifies deletion completes even when legacy mirror cleanup throws an exception

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[github-actions]

Thanks for your this PR. 🙏
Please check again for your PR changes whether contains any usage/api/configuration change such as Add new API , Add new configuration, Change default value of configuration.
If so, please add or update documents(markdown type) in docs/next/ for repository nacos-group/nacos-group.github.io

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感谢您提交的PR。 🙏
请再次查看您的PR内容，确认是否包含任何使用方式/API/配置参数的变更，如：新增API、新增配置参数、修改默认配置等操作。
如果是，请确保在提交之前，在仓库nacos-group/nacos-group.github.io中的docs/next/目录下添加或更新文档（markdown格式）。

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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