- Add GitHub Actions workflow to run backend (pytest) and frontend
(vitest) tests on PRs and pushes to main
- Replace hardcoded locale parity tests with dynamic discovery from
the resources registry, so new languages are tested automatically
- Add unused key detection test that scans source files for i18n
key references, with optional chaining normalization
- Remove 149 genuinely unused translation keys from all 7 locale files
- Add missing keys to it-IT (7) and ru-RU (5) with English fallback
