Fix build prod : Pinia CJS default import crash Node 22+

Pinia résout vers pinia.prod.cjs en production, Rollup convertit
require('vue') en default import ESM invalide. Script post-build
remplace par un namespace import (* as).

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

package.json

@@ -3,7 +3,7 @@
   "type": "module",
   "private": true,
   "scripts": {
-    "build": "nuxt build",
+    "build": "nuxt build && node scripts/fix-esm-imports.mjs",
     "dev": "nuxt dev",
     "generate": "nuxt generate",
     "preview": "nuxt preview",