fix: restore govuk-frontend to dependencies; peer dep is additive not a replacement

Author: alexluckett

package.json

@@ -131,7 +131,8 @@
     "pino-pretty": "^13.1.3",
     "proxy-agent": "^6.5.0",
     "resolve": "^1.22.12",
-    "yaml": "^2.9.0"
+    "yaml": "^2.9.0",
+    "govuk-frontend": "^6.2.0"
   },
   "devDependencies": {
     "@babel/cli": "^7.29.7",
@@ -202,8 +203,7 @@
     "typescript-eslint": "^8.56.1",
     "webpack": "^5.107.2",
     "webpack-assets-manifest": "^6.5.2",
-    "webpack-cli": "^7.0.3",
-    "govuk-frontend": "^6.2.0"
+    "webpack-cli": "^7.0.3"
   },
   "peerDependencies": {
     "govuk-frontend": "^6.0.0"