feat(frontend): c2 config card + execute modal (sprint 8 phase 1)

- frontend/src/api/c2.ts: 6 typed API calls (getC2Config, putC2Config,
  deleteC2Config, testC2Config, listCallbacks, executeC2) following the
  frozen M1+M2 backend contracts
- frontend/src/api/types.ts: C2Config, C2ConfigInput, C2TestResult,
  C2Callback, C2CallbacksResponse, C2Task, C2ExecuteInput, C2ExecuteResponse
- frontend/src/hooks/useC2.ts: useC2Config, useUpdateC2Config,
  useDeleteC2Config, useTestC2Config, useC2Callbacks, useExecuteC2
- frontend/src/components/C2ConfigCard.tsx: engagement-scoped C2 config
  card (url + write-only token + verify-tls + save/delete/test-connection),
  503 disabled state, ConfirmDialog on delete
- frontend/src/components/ExecuteViaC2Modal.tsx: callback picker table
  (mono data cells), commands textarea pre-filled from rt.commands,
  Launch disabled until row selected + non-empty commands
- frontend/src/pages/EngagementFormPage.tsx: embed C2ConfigCard in edit
  mode only, admin+redteam only (canEditEngagements gate)
- frontend/src/pages/SimulationFormPage.tsx: Execute via C2 button in RT
  card, visible only when !isDone && canEditRT && hasC2Config; opens modal
- Tests: 33 new tests across api/c2, components/C2ConfigCard,
  components/ExecuteViaC2Modal, EngagementFormPage, SimulationFormPage
  (172 total, 139 baseline + 33 new, all passing)

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

frontend/src/hooks/useC2.ts

@@ -0,0 +1,81 @@
+import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
+import {
+  deleteC2Config,
+  executeC2,
+  getC2Config,
+  listCallbacks,
+  putC2Config,
+  testC2Config,
+} from '@/api/c2';
+import type { C2ConfigInput, C2ExecuteInput } from '@/api/types';
+
+function c2ConfigKey(engagementId: number) {
+  return ['c2-config', engagementId] as const;
+}
+
+function c2CallbacksKey(engagementId: number) {
+  return ['c2-callbacks', engagementId] as const;
+}
+
+function simulationKey(id: number) {
+  return ['simulations', id] as const;
+}
+
+export function useC2Config(engagementId: number | undefined, options?: { enabled?: boolean }) {
+  const enabled =
+    typeof engagementId === 'number' &&
+    !Number.isNaN(engagementId) &&
+    (options?.enabled !== false);
+
+  return useQuery({
+    queryKey: engagementId ? c2ConfigKey(engagementId) : ['c2-config', 'none'],
+    queryFn: () => getC2Config(engagementId as number),
+    enabled,
+  });
+}
+
+export function useUpdateC2Config(engagementId: number) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (input: C2ConfigInput) => putC2Config(engagementId, input),
+    onSuccess: () => qc.invalidateQueries({ queryKey: c2ConfigKey(engagementId) }),
+  });
+}
+
+export function useDeleteC2Config(engagementId: number) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: () => deleteC2Config(engagementId),
+    onSuccess: () => qc.invalidateQueries({ queryKey: c2ConfigKey(engagementId) }),
+  });
+}
+
+export function useTestC2Config(engagementId: number) {
+  return useMutation({
+    mutationFn: () => testC2Config(engagementId),
+  });
+}
+
+export function useC2Callbacks(engagementId: number | undefined, options?: { enabled?: boolean }) {
+  const enabled =
+    typeof engagementId === 'number' &&
+    !Number.isNaN(engagementId) &&
+    (options?.enabled !== false);
+
+  return useQuery({
+    queryKey: engagementId ? c2CallbacksKey(engagementId) : ['c2-callbacks', 'none'],
+    queryFn: () => listCallbacks(engagementId as number),
+    enabled,
+  });
+}
+
+export function useExecuteC2(simulationId: number, engagementId: number) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (input: C2ExecuteInput) => executeC2(simulationId, input),
+    onSuccess: () => {
+      qc.invalidateQueries({ queryKey: simulationKey(simulationId) });
+      qc.invalidateQueries({ queryKey: ['engagements', engagementId, 'simulations'] });
+    },
+  });
+}