Adding Lightdash integration documentation

[torimwhaley]

Summary

This PR adds a new Lightdash integration page under docs/integrations/data-visualization/.
It documents how to connect Lightdash — an open-source BI platform built on dbt — to ClickHouse for fast, governed analytics.

Changes include:

• New guide: lightdash-and-clickhouse.md
• Added Lightdash entry to the data visualization section in sidebars.js
• Added Lightdash logo in static/images/integrations/logos/lightdash.png

This addition helps users discover and connect ClickHouse with Lightdash directly from the official ClickHouse integrations hub.

Checklist

• Delete items not relevant to your PR
• URL changes should add a redirect to the old URL via https://github.com/ClickHouse/clickhouse-docs/blob/main/docusaurus.config.js
• If adding a new integration page, also add an entry to the integrations list here: https://github.com/ClickHouse/clickhouse-docs/blob/main/docs/integrations/index.mdx

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