fix(campaigns): start_date modal + hide future-campaign tests from queue

Backend: activate endpoint returns 409 with structured warning when
start_date is in the future; accepts force=true to bypass.
test_crud_service: always excludes tests from draft campaigns with future
start_date so they do not appear in the team queue prematurely.

Frontend: catches 409 on activate and shows amber confirmation modal
with Keep scheduled / Activate now anyway options.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api/campaigns.ts

@@ -134,8 +134,12 @@ export async function removeTestFromCampaign(
 }
 
 /** Activate a campaign. */
-export async function activateCampaign(campaignId: string): Promise<Campaign> {
-  const { data } = await client.post<Campaign>(`/campaigns/${campaignId}/activate`);
+export async function activateCampaign(
+  campaignId: string,
+  options?: { force?: boolean },
+): Promise<Campaign> {
+  const params = options?.force ? "?force=true" : "";
+  const { data } = await client.post<Campaign>(`/campaigns/${campaignId}/activate${params}`);
   return data;
 }
 

frontend/src/pages/CampaignDetailPage.tsx

@@ -68,6 +68,8 @@ export default function CampaignDetailPage() {
   const [showAddTestModal, setShowAddTestModal] = useState(false);
   // 0 = hidden, 1 = first confirmation, 2 = ask about tests
   const [deleteStep, setDeleteStep] = useState<0 | 1 | 2>(0);
+  // Start-date confirmation modal — shown when campaign has a future start_date
+  const [startDateWarning, setStartDateWarning] = useState<string | null>(null);
 
   const showToast = (message: string, type: "success" | "error") => {
     setToast({ message, type });
@@ -89,12 +91,21 @@ export default function CampaignDetailPage() {
   });
 
   const activateMutation = useMutation({
-    mutationFn: () => activateCampaign(campaignId!),
+    mutationFn: (force = false) => activateCampaign(campaignId!, force ? { force: true } : undefined),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ["campaign", campaignId] });
+      setStartDateWarning(null);
       showToast("Campaign activated", "success");
     },
-    onError: (err: Error) => showToast(err.message, "error"),
+    onError: (err: unknown) => {
+      // 409 = future start_date warning → show confirmation modal instead of toast
+      const axiosErr = err as { response?: { status?: number; data?: { message?: string; start_date?: string } } };
+      if (axiosErr?.response?.status === 409 && axiosErr.response.data?.message) {
+        setStartDateWarning(axiosErr.response.data.message);
+      } else {
+        showToast((err as Error).message, "error");
+      }
+    },
   });
 
   const completeMutation = useMutation({
@@ -297,7 +308,7 @@ export default function CampaignDetailPage() {
             )}
             {canManage && campaign.status === "draft" && (
               <button
-                onClick={() => activateMutation.mutate()}
+                onClick={() => activateMutation.mutate(false)}
                 disabled={activateMutation.isPending}
                 className="flex items-center gap-1.5 rounded-lg bg-cyan-600 px-4 py-2 text-sm font-medium text-white hover:bg-cyan-500 disabled:opacity-50 transition-colors"
               >
@@ -666,6 +677,37 @@ export default function CampaignDetailPage() {
         onSuccess={() => showToast("Test added to campaign", "success")}
       />
 
+      {/* Start-date confirmation modal */}
+      {startDateWarning && (
+        <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/70 backdrop-blur-sm">
+          <div className="mx-4 w-full max-w-md rounded-xl border border-amber-500/30 bg-gray-900 p-6 shadow-2xl">
+            <div className="mb-4 flex items-center gap-3">
+              <div className="rounded-lg bg-amber-500/10 p-2">
+                <Clock className="h-5 w-5 text-amber-400" />
+              </div>
+              <h3 className="text-lg font-semibold text-white">Campaign not started yet</h3>
+            </div>
+            <p className="mb-6 text-sm text-gray-300 leading-relaxed">{startDateWarning}</p>
+            <div className="flex justify-end gap-3">
+              <button
+                onClick={() => setStartDateWarning(null)}
+                className="rounded-lg border border-gray-700 px-4 py-2 text-sm text-gray-400 hover:bg-gray-800 transition-colors"
+              >
+                Keep scheduled
+              </button>
+              <button
+                onClick={() => activateMutation.mutate(true)}
+                disabled={activateMutation.isPending}
+                className="flex items-center gap-1.5 rounded-lg bg-amber-600 px-4 py-2 text-sm font-medium text-white hover:bg-amber-500 disabled:opacity-50 transition-colors"
+              >
+                {activateMutation.isPending && <Loader2 className="h-4 w-4 animate-spin" />}
+                Activate now anyway
+              </button>
+            </div>
+          </div>
+        </div>
+      )}
+
       {/* Toast notification */}
       {toast && (
         <div