test(web): add example frontend tests (#61)
* test(web): setup frontend test infrastructure
- Add testing dependencies (vitest, vue-test-utils, testing-library, jsdom, msw)
- Create vitest.config.ts with jsdom environment and coverage settings
- Create setup.ts with Pinia initialization and fake timers
- Add test scripts to package.json (test, test:run, test:coverage)
Closes #56, closes #57
* test(web): add example frontend tests
- Add system store tests (initial state, getters, togglePause)
- Add eventHelper utility tests (processNewEvents, mergeAndSortEvents, avatarIdToColor, highlightAvatarNames)
Closes #59