- Extract six pure tag-related functions from dashboard.js into new server/services/TagMatcher.js
- Functions: sanitizeTagLabel, tagMatchesUser, extractAllTags, extractUserTag, getEmbyUsers, buildTagBadges
- Update dashboard.js to import TagMatcher and replace all inline function calls
- Add comprehensive unit tests in tests/unit/services/TagMatcher.test.js (26 tests passing for 5 pure functions)
- Note: getEmbyUsers tests excluded due to CommonJS mocking complexity
