docs: style cpp-rs api reference

[dgarcia360]

Related scylladb/sphinx-scylladb-theme#1516

Updates API reference look and feel:

How to test

1. Build the docs.
2. Open the API reference.
3. Review the new UI at http://127.0.0.1:5500/api/

[dgarcia360]

cc/ @annastuchlik

[Copilot]

Pull request overview

This PR updates the styling and build configuration for the CPP-Rust Driver's API reference documentation. The changes aim to improve the look and feel of the API documentation by adjusting the table of contents depth and optimizing the preview workflow.

Key changes:

• Reduced API documentation table of contents depth from 2 to 1 for a cleaner appearance
• Added ignore pattern for auto-generated API files in the documentation preview command

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/source/api/index.rst	Reduced maxdepth from 2 to 1 to simplify the API documentation navigation hierarchy
docs/Makefile	Added --ignore flag to skip watching auto-generated API files during live preview, improving build performance

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[Lorak-mmk]

In the sidebar, each method name is prefixed with the ClassName::. This isn't really necessary - the methods are already in the section about the class, as indicated by the indentation level:

This causes more line wrapping than would be otherwise necessary, maybe it would be more readable to drop the prefix?

[dgarcia360]

@Lorak-mmk removed the prefix in 3ded240