fix: resolve Docker build failures for frontend

- Remove @radix-ui/react-badge (package inexistant sur npm) du package.json
- Rename next.config.ts → next.config.mjs (Next.js 14 ne supporte pas .ts)
- Générer package-lock.json requis par npm ci dans le Dockerfile
- Ajouter next-env.d.ts (généré par Next.js build, requis pour TypeScript)

Build Next.js vérifié : 6 pages générées (/, /login, /dashboard, /clients, /audits)

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

frontend/package.json

@@ -14,7 +14,6 @@
     "react": "^18",
     "react-dom": "^18",
     "@radix-ui/react-avatar": "^1.0.4",
-    "@radix-ui/react-badge": "^1.0.0",
     "@radix-ui/react-dialog": "^1.0.5",
     "@radix-ui/react-dropdown-menu": "^2.0.6",
     "@radix-ui/react-label": "^2.0.2",