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.

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

frontend/src/components/Sidebar.tsx

@@ -1,5 +1,6 @@
 import { NavLink } from "react-router-dom";
 import { useState } from "react";
+import { useQuery } from "@tanstack/react-query";
 import {
   LayoutDashboard,
   FlaskConical,
@@ -19,8 +20,10 @@ import {
   ShieldCheck,
   GitCompareArrows,
   ScrollText,
+  ClipboardCheck,
 } from "lucide-react";
 import { useAuth } from "../context/AuthContext";
+import { getTechniques } from "../api/techniques";
 
 interface NavItem {
   to: string;
@@ -35,6 +38,7 @@ const mainLinks: NavItem[] = [
   { to: "/dashboard", label: "Dashboard", icon: LayoutDashboard },
   { to: "/executive-dashboard", label: "Executive Dashboard", icon: Gauge, roles: ["admin", "red_lead", "blue_lead", "viewer"] },
   { to: "/matrix", label: "ATT&CK Matrix", icon: Grid3X3 },
+  { to: "/techniques/review-queue", label: "Review Queue", icon: ClipboardCheck, roles: ["admin", "red_lead", "blue_lead"] },
   {
     to: "/tests",
     label: "Tests",
@@ -60,7 +64,7 @@ const systemLinks: NavItem[] = [
   { to: "/audit", label: "Audit Log", icon: FileText },
 ];
 
-function SidebarLink({ item }: { item: NavItem }) {
+function SidebarLink({ item, badge }: { item: NavItem; badge?: number }) {
   const [expanded, setExpanded] = useState(false);
 
   if (item.children) {
@@ -104,6 +108,7 @@ function SidebarLink({ item }: { item: NavItem }) {
   return (
     <NavLink
       to={item.to}
+      end
       className={({ isActive }) =>
         `flex items-center gap-3 rounded-lg px-3 py-2.5 text-sm font-medium transition-colors ${
           isActive
@@ -112,8 +117,13 @@ function SidebarLink({ item }: { item: NavItem }) {
         }`
       }
     >
-      <item.icon className="h-5 w-5" />
-      {item.label}
+      <item.icon className="h-5 w-5 shrink-0" />
+      <span className="flex-1">{item.label}</span>
+      {badge !== undefined && badge > 0 && (
+        <span className="rounded-full bg-amber-500 px-1.5 py-0.5 text-[10px] font-bold text-white leading-none">
+          {badge}
+        </span>
+      )}
     </NavLink>
   );
 }
@@ -123,10 +133,22 @@ export default function Sidebar() {
   const role = user?.role ?? "";
   const isAdmin = role === "admin";
 
+  const canSeeReviewQueue =
+    isAdmin || role === "red_lead" || role === "blue_lead";
+
+  // Fetch review queue count for the badge (only for roles that can see it)
+  const { data: reviewQueue } = useQuery({
+    queryKey: ["techniques", "review-queue"],
+    queryFn: () => getTechniques({ review_required: true }),
+    enabled: canSeeReviewQueue,
+    staleTime: 5 * 60 * 1000, // 5 min — don't hammer the API
+  });
+  const reviewCount = reviewQueue?.length ?? 0;
+
   /** Returns true when the current user is allowed to see `item`. */
   const canSee = (item: NavItem) => {
-    if (!item.roles) return true;          // no restriction
-    if (isAdmin) return true;              // admin sees everything
+    if (!item.roles) return true;
+    if (isAdmin) return true;
     return item.roles.includes(role);
   };
 
@@ -143,7 +165,11 @@ export default function Sidebar() {
       {/* Main nav */}
       <nav className="flex-1 space-y-1 overflow-y-auto px-3 py-4">
         {mainLinks.filter(canSee).map((item) => (
-          <SidebarLink key={item.to + item.label} item={item} />
+          <SidebarLink
+            key={item.to + item.label}
+            item={item}
+            badge={item.to === "/techniques/review-queue" ? reviewCount : undefined}
+          />
         ))}
 
         {/* System / Administration section — admin only */}