Add unit, integration and e2e test suites

tests/{unit,integration,e2e}/, at the repo root (not under frontend/,
since e2e exercises the frontend and PocketBase together) — all
against real code rather than mocks:

- unit/: Vitest (nuxt environment) — pure functions in server/utils
  and shared/utils, plus components/composables via
  @nuxt/test-utils/runtime's mountSuspended.
- integration/: Vitest (node environment) — @nuxt/test-utils/e2e's
  setup() builds and runs the real Nitro server against a real
  ephemeral PocketBase instance, exercising the actual /content/* and
  /admin routes end to end.
- e2e/: Playwright, a real browser against the built app and another
  ephemeral PocketBase, covering the user-facing flows (home, blog
  archive, article detail incl. JSON-LD, category filter, 404s, the
  /admin redirect).

The Vitest/Playwright tooling (and node_modules) stays in frontend/,
the repo's only npm project; its configs just point at ../tests/.
Playwright resolves packages from the node_modules nearest each spec
file, so `npm run test:e2e` first symlinks tests/node_modules to
frontend/node_modules (pretest:e2e, idempotent, gitignored).

tests/support/pocketbase.ts is the shared piece behind integration
and e2e: it downloads the same pinned PocketBase binary
pocketbase/Dockerfile uses, starts it against the real
pocketbase/pb_migrations/ (not a copy), and seeds it from
tests/support/fixtures.ts — so these tests run against the exact
schema and API rules that ship to production, catching the class of
bug that only shows up when PocketBase actually enforces them (e.g. a
wrong filter/fields query string silently returning nothing, or too
much).

CLAUDE.md and docs/frontend.md document the new npm scripts and the
single-test commands for each layer.

CLAUDE.md

@@ -10,8 +10,8 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Stato
 
-Struttura, content type, pagine blog, Docker e Caddy sono in piedi. Restano da fare:
-sitemap e `robots.txt` dinamici, ricerca, e i test (nessun framework ancora configurato).
+Struttura, content type, pagine blog, Docker, Caddy e i test (unit/integration/e2e) sono in
+piedi. Restano da fare: sitemap e `robots.txt` dinamici, ricerca.
 
 ## Architettura
 
@@ -67,6 +67,16 @@ npm run build      # build produzione
 npm run typecheck  # nuxi typecheck — obbligatorio prima di dichiarare fatto
 npm run lint
 
+npm run test:unit         # Vitest, ambiente Nuxt: funzioni pure + componenti/composable
+npm run test:integration  # Vitest, server Nitro reale + PocketBase effimero reale
+npm run test:e2e          # Playwright, browser reale contro build + PocketBase effimero reale
+npm run test               # i tre, in sequenza
+
+# singolo test:
+npx vitest run --config vitest.unit.config.ts tests/unit/queries.utils.test.ts
+npx vitest run --config vitest.integration.config.ts -t "lists only published articles"
+npx playwright test tests/e2e/home.spec.ts
+
 # pocketbase/ (nessun npm script: binario singolo, le migration si applicano da sole all'avvio)
 docker compose -f docker-compose.yml -f docker-compose.dev.yml up -d --build pocketbase frontend
 
@@ -81,8 +91,17 @@ docker compose -f docker-compose.yml -f docker-compose.dev.yml up -d --build poc
 `docker-compose.dev.yml` va passato **sempre esplicitamente**: non è un `override.yml` proprio
 per non finire per sbaglio in produzione esponendo le porte.
 
-Nessun test framework è ancora configurato. Se ne aggiungi uno, documenta qui il comando per
-lanciare **un singolo test**.
+`tests/` sta nella root del repo (non sotto `frontend/`), perché l'e2e esercita frontend e
+PocketBase insieme — gli strumenti (config Vitest/Playwright, `node_modules`) restano comunque in
+`frontend/`, l'unico progetto npm del repo, e puntano a `../tests/`. Playwright risolve i pacchetti
+dal `node_modules` più vicino al file di test: per questo `npm run test:e2e` crea prima (script
+`pretest:e2e`, idempotente) il symlink `tests/node_modules → ../frontend/node_modules`.
+
+I test di integration/e2e avviano un vero binario PocketBase effimero (scaricato una volta in
+`.cache/pocketbase/` nella root, versione allineata a `pocketbase/Dockerfile`) contro le vere
+migration in `pocketbase/pb_migrations/` — niente PocketBase mockato. `npm run test:e2e` richiede
+Chromium installato una tantum: `npx playwright install chromium` (senza `--with-deps`, che
+richiede `sudo`; se mancano librerie di sistema per il browser, installarle a parte).
 
 ## Modelli di contenuto