fix: version dropdown regex + Pages deploy for archived builds

[leseb]

Summary

• Fix Pages deploy for archived versions: Removed BUILDING_LATEST gate from the Pages artifact upload and deploy steps so archived version builds (e.g., v0.7.0) actually get deployed to GitHub Pages
• Add version dropdown to navbar: Replaced the non-functional docsVersionDropdown with a custom dropdown populated from versionsArchived.json — latest build shows "main (unreleased)", archived builds show their version tag
• Fix dropdown regex: The previous regex stopped at the inner }, of dropdownItemsAfter instead of the outer block, causing a TypeScript parse error. Anchored to the 8-space-indented closing brace instead.

Test plan

• Trigger an archived version build (e.g., v0.7.0) and verify the build succeeds (no parse error)
• Verify the Pages deploy step runs and the archived version is accessible at its URL
• Trigger a latest build and verify the version dropdown appears with all archived versions
• On an archived version page, verify the dropdown shows the version tag with links to main and other versions

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