test: setup Vitest workspace and Playwright with first nutrition tests

Vitest:
- Workspace at root (vitest.workspace.ts) running per-package configs
- packages/shared/vitest.config.ts with v8 coverage and 70% thresholds
- Root scripts: test / test:watch / test:coverage

Nutrition module in @ketopath/shared:
- calculateBmr (Mifflin-St Jeor) + calculateTdee with activity multipliers
- ACTIVITY_MULTIPLIERS constants matching CLAUDE.md domain knowledge
- 14 unit tests covering Michele/Laura PRD personas, all sex variants,
  every activity level, and input validation (100% coverage on src/nutrition)

Playwright in apps/web:
- chromium-only project, webServer auto-boot of pnpm dev
- e2e/home.spec.ts smoke test asserts Italian copy and disclaimer

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -19,7 +19,9 @@
     "format": "prettier --write .",
     "format:check": "prettier --check .",
     "typecheck": "tsc -b",
-    "test": "pnpm --filter \"./packages/*\" --filter \"./apps/*\" -r --if-present test",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "test:coverage": "vitest run --coverage",
     "test:e2e": "pnpm --filter @ketopath/web test:e2e",
     "db:generate": "pnpm --filter @ketopath/db db:generate",
     "db:migrate": "pnpm --filter @ketopath/db db:migrate",
@@ -40,7 +42,9 @@
     "lint-staged": "^15.2.2",
     "prettier": "^3.2.5",
     "prettier-plugin-tailwindcss": "^0.5.14",
-    "typescript": "5.4.5"
+    "typescript": "5.4.5",
+    "vitest": "^1.6.0",
+    "@vitest/coverage-v8": "^1.6.0"
   },
   "lint-staged": {
     "*.{ts,tsx,js,jsx,cjs,mjs}": [