docs: add OrcaRouterChatGenerator documentation page

[jinhaosong-source]

Summary

• Adds a dedicated documentation page for the OrcaRouterChatGenerator integration under docs-website/docs/pipeline-components/generators/
• Adds OrcaRouter to the generators overview table and the sidebar navigation
• Mirrors the same additions into the latest versioned docs (version-2.30)

The orcarouter-haystack package is already published (PyPI: https://pypi.org/project/orcarouter-haystack/), and the integration page PR is deepset-ai/haystack-integrations#537.

Follow-up to deepset-ai/haystack-core-integrations#3436, as requested by @anakin87.

[vercel]

@Tab2332 is attempting to deploy a commit to the deepset Team on Vercel.

A member of the Team first needs to authorize it.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}