chore: add web-test-runner for react-auth

[Lodin]

Fixes test failures in #2901 by replacing Karma Test Runner (deprecated) with Web Test Runner.

Web Test Runner is applied only to the react-auth package. The plan is to incrementally transfer other browser-based packages over time.

[sonarcloud]

Quality Gate failed

Failed conditions
3.1% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud

[Lodin]

Please ignore SonarCloud results. The code duplication is expected because there is some files moved out of karma.config.js and placed in TypeScript files. Since Karma is unable to work with TS, I had to keep both versions. When we move to WTR completely, the duplication will be gone.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.89%. Comparing base (e2af537) to head (c1161f9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2926      +/-   ##
==========================================
+ Coverage   92.64%   92.89%   +0.24%     
==========================================
  Files          83       83              
  Lines        2857     3137     +280     
  Branches      744      757      +13     
==========================================
+ Hits         2647     2914     +267     
- Misses        157      171      +14     
+ Partials       53       52       -1     

Flag	Coverage Δ
unittests	92.89% <ø> (+0.24%)	⬆️

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