feat: Phase 7 - Frontend scaffolding and auth (T-023, T-024, T-025)

T-023: Initialize React project
- Vite + React 19 + TypeScript scaffold
- Tailwind CSS v4 with @tailwindcss/vite plugin
- Dependencies: react-router-dom, axios, @tanstack/react-query, lucide-react
- Project structure: api/, components/, pages/, context/, types/, hooks/, lib/

T-024: API client and auth context
- Axios client with JWT interceptor (auto-attach token, clear on 401)
- login() and getMe() API functions
- AuthContext: user state, login, logout, isAuthenticated, isLoading
- Token persistence via localStorage with hydration on mount
- TypeScript types for all backend models

T-025: Login page and layout
- LoginPage with form, error handling, redirect on success
- Layout with sidebar + header + Outlet
- Sidebar with role-aware navigation (System only for admin)
- ProtectedRoute wrapper with role-based access control
- Routes: /login, /dashboard, /techniques, /tests, /system

frontend/src/components/Layout.tsx

@@ -0,0 +1,33 @@
+import { Outlet } from "react-router-dom";
+import { LogOut } from "lucide-react";
+import { useAuth } from "../context/AuthContext";
+import Sidebar from "./Sidebar";
+
+export default function Layout() {
+  const { user, logout } = useAuth();
+
+  return (
+    <div className="flex h-screen bg-gray-950 text-gray-100">
+      <Sidebar />
+
+      <div className="flex flex-1 flex-col overflow-hidden">
+        {/* Header */}
+        <header className="flex h-16 items-center justify-end gap-4 border-b border-gray-800 bg-gray-900 px-6">
+          <span className="text-sm text-gray-300">{user?.username}</span>
+          <button
+            onClick={logout}
+            className="flex items-center gap-1.5 rounded-lg px-3 py-1.5 text-sm text-gray-400 transition-colors hover:bg-gray-800 hover:text-white"
+          >
+            <LogOut className="h-4 w-4" />
+            Logout
+          </button>
+        </header>
+
+        {/* Main content */}
+        <main className="flex-1 overflow-y-auto p-6">
+          <Outlet />
+        </main>
+      </div>
+    </div>
+  );
+}