docs migration - Swift on Server Guides index

Source: documentation/server/guides/index.md
Proposed disposition: Migrate — translate and use as the root article / overview for ServerGuides.docc.
Proposed destination: Top-level overview content in server-guides/Sources/ServerGuides.docc/Documentation.md (or a dedicated index.md article linked from Documentation.md)
Reviewer: @swiftlang/server-workgroup

Checklist

• Create a GitHub issue to track this migration
• Determine disposition (suggested: Migrate) and confirm destination
• Review source for accuracy; update the list of guides to reflect what is actually in the catalog after other server guide articles migrate
• Translate Jekyll markdown to DocC markdown format
  • Remove YAML front matter
  • Convert any Jekyll callouts to DocC-style callouts
  • Replace hard-coded links to individual guides with DocC topic group references
• Incorporate content into ServerGuides.docc/Documentation.md topic structure
• Run swift package generate-documentation --analyze --warnings-as-errors in server-guides/
• Preview locally with swift package --disable-sandbox preview-documentation in server-guides/
• Submit PR to this repository for server workgroup review
• After merge and publication: add redirect_to: in the swift.org source file's front matter
• Submit redirect PR to swift-org-website

Start by reading documentation/server/guides/index.md and server-guides/Sources/ServerGuides.docc/Documentation.md, then inspect the current ServerGuides.docc catalog. Translate the source into DocC, update the topic structure and guide links, run the documented generate-documentation and preview commands, and finish with the server workgroup PR and subsequent redirect PR.