feat(test): implementazione infrastruttura completa (Unit, Integration, E2E) con Vitest e Playwright

- Introduce Vitest per Unit e Integration Test.
- Introduce Playwright per End-to-End Test.
- Aggiuge documentazione dettagliata in tests/README.md.
- Aggiorna .gitignore per escludere i report di coverage

.gitignore

@@ -25,3 +25,13 @@ dist-ssr
 *.njsproj
 *.sln
 *.sw?
+
+# Playwright
+/test-results/
+/playwright-report/
+/blob-report/
+/playwright/.cache/
+/playwright/.auth/
+
+# Vitest
+coverage/