archive(1.3) isolation: remove all other versions, pt 2: reviewable

[pepopowitz]

Part of #2189.

Note: this PR will be merged into the unsupported/1.3 branch. It will never make it into main.

Description

Continues the process of archival/isolation for version 1.3. Many of the steps were done by a computer for me (the src/hacks/isolateVersion script), but the last few are manual:

Progress

• exclude all other versions from the main version file
• exclude all other versions from the optimize version file
• prevent unsupported site from being crawled
• fix Dockerfile for local debugging
• update theme components
• update CI workflows
• update docusaurus config
• configure Optimize docs instance
• fix incorrect URLs
• update rewrite rules based on 1.3 basepath
• figure out how to fix the broken links on the homepage (many link to nonexistent pages in this version)
• figure out if I need to fix the links reported by vale

When should this change go live?

• This is a bug fix, security concern, or something that needs urgent release support.
• This is already available but undocumented and should be released within a week.
• This on a specific schedule and the assignee will coordinate a release with the DevEx team. (apply hold label or convert to draft PR)
• This is part of a scheduled alpha or minor. (apply alpha or minor label)
• There is no urgency with this change and can be released at any time.

PR Checklist

• My changes are for an already released minor and are in /versioned_docs directory.
• My changes are for the next minor and are in /docs directory (aka /next/).

• My changes require an Engineering review, and I've assigned the Engineering DRI or delegate.

• My changes require a technical writer review, and I've assigned @camunda/tech-writers as a reviewer.

• My changes require a docs infrastructure review.

[github-actions]

⚠️ [vale] _{reported by reviewdog 🐶}
[docsInstance.hrefDocsToDocs] Improper link format: 'Camunda Operate'. Please specify the file extension.