feat(review-queue): MITRE update review queue for leads

- New /techniques/review-queue page: lists all techniques flagged for
  review after a MITRE ATT&CK sync, grouped by tactic. Leads and admins
  can mark each one reviewed inline without leaving the page.
- Sidebar: 'Review Queue' link (admin/red_lead/blue_lead only) with an
  amber badge showing the live pending count.
- TechniqueDetailPage: amber banner when review_required=true explaining
  what happened and who can act; 'Mark as Reviewed' button now amber
  coloured for visual distinction. 'Leads only' chip shown for blue_tech.

frontend/src/App.tsx

@@ -19,6 +19,7 @@ const TestCreatePage = React.lazy(() => import("./pages/TestCreatePage"));
 const TestDetailPage = React.lazy(() => import("./pages/TestDetailPage"));
 const TestCatalogPage = React.lazy(() => import("./pages/TestCatalogPage"));
 const ValidatedTestsPage = React.lazy(() => import("./pages/ValidatedTestsPage"));
+const ReviewQueuePage = React.lazy(() => import("./pages/ReviewQueuePage"));
 const ReportsPage = React.lazy(() => import("./pages/ReportsPage"));
 const SystemPage = React.lazy(() => import("./pages/SystemPage"));
 const UsersPage = React.lazy(() => import("./pages/UsersPage"));
@@ -52,6 +53,7 @@ export default function App() {
         <Route path="/techniques/:mitreId" element={<Suspense fallback={<LoadingSpinner text="Loading…" />}><TechniqueDetailPage /></Suspense>} />
 
         <Route path="/matrix" element={<Suspense fallback={<LoadingSpinner text="Loading…" />}><MatrixPage /></Suspense>} />
+        <Route path="/techniques/review-queue" element={<Suspense fallback={<LoadingSpinner text="Loading…" />}><ReviewQueuePage /></Suspense>} />
 
         {/* ── Executive Dashboard (leads + admin) ──────────────── */}
         <Route