Site Overview: Add accessible name to unlaunched site setup progress ring

[p-jackson]

Fixes DOTMSD-1475

Proposed Changes

• Add an ariaLabel prop to the shared CircularProgressBar component and wire the role="progressbar" element with aria-valuemin/aria-valuemax/aria-valuenow/aria-label.
• Pass ariaLabel="Steps to launch your site" from the Site Overview OverviewCard unlaunched-site setup progress ring.

Why are these changes being made?

The 1/4 visibility progress ring on Site Overview announced nothing to assistive tech — axe flagged aria-progressbar-name. The role="progressbar" element had no accessible name and no value semantics, so screen readers couldn't convey what it represented or how far along it was. This gives it a name and exposes its min/max/current values.

Testing Instructions

• Open Site Overview for an unlaunched site.
• Inspect the setup progress ring (.circular__progress-bar) and confirm it now has aria-label="Steps to launch your site" plus aria-valuemin/aria-valuemax/aria-valuenow.
• Run axe (or a screen reader) and confirm the aria-progressbar-name violation is gone and the ring announces its label and progress.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• For UI changes, have you tested the affected components in dark mode?
• Have you tested accessibility for your changes? Ensure the feature remains usable with various user agents (e.g., browsers), interfaces (e.g., keyboard navigation), and assistive technologies (e.g., screen readers) (PCYsg-S3g-p2).
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

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[a8ci18n]

This Pull Request is now available for translation here: https://translate.wordpress.com/deliverables/34678102

Some locales (Hebrew, Japanese) have been temporarily machine-translated due to translator availability. All other translations are usually ready within a few days. Untranslated and machine-translated strings will be sent for translation next Monday and are expected to be completed by the following Friday.

Hi @p-jackson, could you please edit the description of this PR and add a screenshot for our translators? Ideally it'd include this string: %1$d of %2$d steps complete

Thank you in advance!