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>

tests/unit/storage.test.js

@@ -0,0 +1,59 @@
+import { describe, it, expect, beforeEach } from 'vitest'
+import { save, load } from '../../src/utils/storage.js'
+
+// localStorage viene svuotato in tests/setup.js — qui garantiamo isolamento locale
+beforeEach(() => localStorage.clear())
+
+describe('save', () => {
+  it('serializza un oggetto in JSON', () => {
+    save('test', { a: 1, b: 'due' })
+    expect(localStorage.getItem('test')).toBe('{"a":1,"b":"due"}')
+  })
+
+  it('serializza un array', () => {
+    save('list', [1, 2, 3])
+    expect(localStorage.getItem('list')).toBe('[1,2,3]')
+  })
+
+  it('sovrascrive un valore esistente', () => {
+    save('key', 'primo')
+    save('key', 'secondo')
+    expect(localStorage.getItem('key')).toBe('"secondo"')
+  })
+
+  it('gestisce valori primitivi (numero, stringa, booleano)', () => {
+    save('n', 42)
+    save('s', 'ciao')
+    save('b', false)
+    expect(JSON.parse(localStorage.getItem('n'))).toBe(42)
+    expect(JSON.parse(localStorage.getItem('s'))).toBe('ciao')
+    expect(JSON.parse(localStorage.getItem('b'))).toBe(false)
+  })
+})
+
+describe('load', () => {
+  it('restituisce il valore parsato se la chiave esiste', () => {
+    localStorage.setItem('obj', '{"a":1}')
+    expect(load('obj', null)).toEqual({ a: 1 })
+  })
+
+  it('restituisce il default se la chiave non esiste', () => {
+    expect(load('nonexistent', 'fallback')).toBe('fallback')
+  })
+
+  it('restituisce il default anche per array vuoto come fallback', () => {
+    expect(load('missing', [])).toEqual([])
+  })
+
+  it('round-trip: save → load restituisce il valore originale', () => {
+    const data = [{ id: 1, name: 'pasta', checked: false }]
+    save('shopping', data)
+    expect(load('shopping', [])).toEqual(data)
+  })
+
+  it('round-trip su struttura pasti annidata', () => {
+    const meals = { lunedi: { colazione: ['caffè'], pranzo: [], cena: [] } }
+    save('meals', meals)
+    expect(load('meals', {})).toEqual(meals)
+  })
+})