fix: render User Guide link correctly inside HTML div block

[slegarraga]

Summary

Fixes #138 — The "User Guide" markdown link inside the <div align="center"> block was not rendering as a clickable hyperlink because markdown syntax is not processed inside HTML block elements per the CommonMark specification.

Changes

Converted the markdown link to an HTML <a> tag in the integrations section:

- Please refer to the [User Guide](https://www.oceanbase.ai/docs/seekdb-overview/) for more details.
+ Please refer to the <a href="https://www.oceanbase.ai/docs/seekdb-overview/">User Guide</a> for more details.

The other "User Guide" link (line 263, inside a <details> block after a code fence closing) already renders correctly since it's outside the HTML block context.

[CLAassistant]

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[hnwyllmm]

Hi @slegarraga. Thanks for your contribution, but please sign the CLA first.