fix(admin-web): lock Next.js to exact version 15.1.11 for CVE-2025-55182 fix

Remove ^ to prevent npm from installing vulnerable 15.5.x versions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/admin-web/package.json

@@ -19,7 +19,7 @@
     "axios": "^1.7.9",
     "clsx": "^2.1.1",
     "dayjs": "^1.11.13",
-    "next": "^15.1.11",
+    "next": "15.1.11",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "react-redux": "^9.2.0",