[stephaniehobson]

Replaces #475, which was approved but merged into react-18-upgrade after that branch had already merged into main, so its change never reached main. This is the same commit, rebased onto main without conflicts.

One-line summary

Fix the heading levels that skip on /contact and on dashboards that have no Summary section.

Significant changes and points to review

• Contact.jsx: add a visible "Contact" h2. Before this, the page went from the site h1 straight to the footer's h3s.
• Dashboard.styl: hide the "Metrics" h3 visually instead of with display: none. Screen readers skipped it, so on User Activity and Usage Behavior the metric h4s followed the h2 directly.
  • Hardware wasn't affected, because its visible "Summary" h3 comes first.
• contact.spec.js: check the new heading.
• axe's heading-order check now passes on /, /contact, all three dashboards, and the 404 page.

Issue / Bugzilla link

#181

Testing

Run npm start first.

• Open http://localhost:3000/contact and check a "Contact" heading appears above the email paragraph.
• Open http://localhost:3000/dashboard/user-activity and check the layout hasn't changed. "Metrics" should not be visible.
• With a screen reader or the browser's accessibility tree, check "Metrics" appears as a level-3 heading on that dashboard.

[stephaniehobson]

Approved as #475 but then its merge when sideways.