[Doc]: Documentation is missing for the AI-sensitive column identification feature

[fenyf]

Description

Problem:
The recently added feature for identifying AI-sensitive columns is powerful, but it currently lacks corresponding user documentation. Users are unaware of its existence, or how to configure and use it effectively.
Solution:
This issue proposes to add a new section to the official documentation that explains this feature in detail.

Documentation links

This issue is for creating new documentation, so no link exists yet.

Additional context

No response

[fenyf]

This documentation is being added to support the new feature implemented in the backend repository.
The corresponding backend Pull Request is: oceanbase/odc#4495