dsh-grok-geo: Execute grok-geo brand GEO audit in DSH

`xuboboo/dsh-grok-geo` is an MIT-licensed DSH bundle plugin designed to provide AI search and GEO (Generative Engine Optimization) audit capabilities for a single brand. The plugin supports 17+ mainstream AI search engines (including 8 international and 9 Chinese engines), covering brand visibility, citations/recommendations, competitor comparison, factual accuracy, and content gap analysis. Its workflow includes input collection, validation, search execution, metrics calculation, and report rendering, and it can automatically switch to an offline import mode when `web_search` is unavailable. The plugin itself does not require Python, but script execution relies on the Python 3.11+ standard library. Users can quickly install it via the `dsh plugin` command, and it takes effect after restarting DSH.