chore: Add a11y checks for app layout toolbar

[just-boris]

Description

Related links, issue #, if available: n/a

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.34%. Comparing base (c59e8fd) to head (aca0246).
Report is 12 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3030   +/-   ##
=======================================
  Coverage   96.34%   96.34%           
=======================================
  Files         780      780           
  Lines       21921    21922    +1     
  Branches     7097     7098    +1     
=======================================
+ Hits        21119    21120    +1     
  Misses        795      795           
  Partials        7        7           

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[just-boris]

Moved into #3063