Update NHS frontend (#282)

This updates the NHS frontend version specified in the package-lock to
10.4, but keeps the minimum version in peerDependencies as `10.3`.

Also adds it to `devDependencies`.

Author: frankieroberto

package-lock.json

@@ -77,6 +77,7 @@
     "eslint-plugin-promise": "^7.2.1",
     "express": "^5.2.1",
     "globals": "^17.4.0",
+    "nhsuk-frontend": "^10.4.0",
     "nunjucks": "^3.2.4",
     "prettier": "^3.8.1",
     "supertest": "7.2.2",
@@ -110,6 +111,6 @@
   ],
   "engines": {
     "node": "^22.16.0 || ^24.11.0",
-    "npm": "^11.6.1"
+    "npm": "^11.6.1 <11.6.3 || ^11.6.4"
   }
 }