Update and restructure MySQL integration docs

[alistairmatthews]

The existing MySQL integration document is comprehensive but difficult for beginners. This PR is intended to keep the comprehensive information but make it easier for those who want to get going quickly. I've used Copilot to propagate changes from the new PostgreSQL documents to the MySQL ones.

This PR:

• Splits the large integration doc into two: Hosting and Client.
• Adds a getting started short tutorial.
• Adds a getting started tutorial for both hosting and client integration.
• Adds a Properties of the PostgreSQL resources section to the client reference docs. This describes what configuration values are injected by the WithReference() method.

[alistairmatthews]

Just want to do some more code testing before this is ready for review.

[Copilot]

Pull request overview

This PR restructures the MySQL integration documentation to improve accessibility for beginners while maintaining comprehensive reference information. It follows a similar pattern to recent PostgreSQL documentation updates, splitting content into separate guides for hosting and client integrations and adding a streamlined getting started tutorial.

Key changes:

• Splits the monolithic MySQL integration document into separate hosting (AppHost) and client integration guides
• Adds a new getting started tutorial with multi-language support (C#, Python, JavaScript)
• Introduces a "Properties of the MySQL resources" reference section documenting injected configuration values

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
mysql-host.mdx	Refactored to focus exclusively on hosting integration (AppHost); removed client integration content and updated cross-references
mysql-get-started.mdx	New comprehensive getting started guide with examples for C#, Python, and JavaScript projects
mysql-client.mdx	New client integration reference including properties tables, configuration options, and observability details
mysql-extensions.mdx	Updated internal links to match new documentation structure
sidebar.topics.ts	Reorganized MySQL section with new four-part structure: Get started, Hosting, Client, and Extensions

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[alistairmatthews]

Closing and reopening to trigger a recheck.