fix(campaigns): reset modification-request modal state on close, not just on success

Previously action/testId/justification only reset inside the success
handler, so cancelling and reopening the modal left stale form values.
Mirrors the reset-on-close pattern already used by AddTestToCampaignModal.

frontend/src/components/RequestCampaignModificationModal.tsx

@@ -1,4 +1,4 @@
-import { useState } from "react";
+import { useEffect, useState } from "react";
 import { useMutation, useQueryClient } from "@tanstack/react-query";
 import { X, Loader2 } from "lucide-react";
 import { createModificationRequest, type CampaignTest } from "../api/campaigns";
@@ -23,6 +23,14 @@ export default function RequestCampaignModificationModal({
   const [testId, setTestId] = useState("");
   const [justification, setJustification] = useState("");
 
+  useEffect(() => {
+    if (!open) {
+      setAction("remove_test");
+      setTestId("");
+      setJustification("");
+    }
+  }, [open]);
+
   const mutation = useMutation({
     mutationFn: () =>
       createModificationRequest(campaignId, {
@@ -32,8 +40,6 @@ export default function RequestCampaignModificationModal({
       }),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ["campaign-modification-requests", campaignId] });
-      setTestId("");
-      setJustification("");
       onSuccess();
       onClose();
     },