chore: add node >=24 constraint to renovate config (#2831)

Adds constraints.node >= 24 to renovate.json so Renovate generates lock files with npm 11 (Node 24).

Reviewed-on: https://gitea.unbound.se/dancefinder/dancefinder-app/pulls/2831

renovate.json

@@ -17,5 +17,8 @@
         "stylelint-config-standard"
       ]
     }
-  ]
+  ],
+  "constraints": {
+    "node": ">=24"
+  }
 }