test: aggiungi suite completa unit, integration ed e2e

- Unit (12+9): conversion.js (rawToCooked/cookedToRaw, edge case, inversa)
  e storage.js (save/load, round-trip, default fallback)
- Integration (17+12+14): Converter (ricerca, selezione, calcolo, swap, reset),
  MealPlanner (rendering, add/remove, generateShopping, deduplicazione),
  ShoppingList (add, toggle, remove, clearAll, contatore)
- E2E Playwright (6+6+7+10): navigation, meal-planner, converter, shopping-list
- Configurazione: vitest.config.js + playwright.config.js + tests/setup.js
- Script: test, test:coverage, test:e2e, test:e2e:ui

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -5,13 +5,23 @@
   "scripts": {
     "dev": "vite --host",
     "build": "vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest",
+    "test:coverage": "vitest --coverage",
+    "test:e2e": "playwright test",
+    "test:e2e:ui": "playwright test --ui"
   },
   "dependencies": {
     "vue": "^3.4.0"
   },
   "devDependencies": {
+    "@playwright/test": "^1.58.2",
     "@vitejs/plugin-vue": "^5.0.0",
-    "vite": "^5.0.0"
+    "@vitest/coverage-v8": "^2.1.9",
+    "@vue/test-utils": "^2.4.6",
+    "happy-dom": "^20.8.9",
+    "jsdom": "^29.0.1",
+    "vite": "^5.0.0",
+    "vitest": "^2.1.9"
   }
 }