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/context/AuthContext.tsx

@@ -0,0 +1,77 @@
+import {
+  createContext,
+  useContext,
+  useEffect,
+  useState,
+  useCallback,
+  type ReactNode,
+} from "react";
+import { login as apiLogin, getMe } from "../api/auth";
+import type { User } from "../types/models";
+
+/* ── Context shape ────────────────────────────────────────────────── */
+
+interface AuthState {
+  user: User | null;
+  isAuthenticated: boolean;
+  isLoading: boolean;
+  login: (username: string, password: string) => Promise<void>;
+  logout: () => void;
+}
+
+const AuthContext = createContext<AuthState | undefined>(undefined);
+
+/* ── Provider ─────────────────────────────────────────────────────── */
+
+export function AuthProvider({ children }: { children: ReactNode }) {
+  const [user, setUser] = useState<User | null>(null);
+  const [isLoading, setIsLoading] = useState(true);
+
+  // On mount — check for a persisted token and hydrate the user
+  useEffect(() => {
+    const token = localStorage.getItem("token");
+    if (!token) {
+      setIsLoading(false);
+      return;
+    }
+
+    getMe()
+      .then(setUser)
+      .catch(() => localStorage.removeItem("token"))
+      .finally(() => setIsLoading(false));
+  }, []);
+
+  const login = useCallback(async (username: string, password: string) => {
+    const token = await apiLogin(username, password);
+    localStorage.setItem("token", token);
+    const me = await getMe();
+    setUser(me);
+  }, []);
+
+  const logout = useCallback(() => {
+    localStorage.removeItem("token");
+    setUser(null);
+  }, []);
+
+  return (
+    <AuthContext.Provider
+      value={{
+        user,
+        isAuthenticated: user !== null,
+        isLoading,
+        login,
+        logout,
+      }}
+    >
+      {children}
+    </AuthContext.Provider>
+  );
+}
+
+/* ── Hook ─────────────────────────────────────────────────────────── */
+
+export function useAuth(): AuthState {
+  const ctx = useContext(AuthContext);
+  if (!ctx) throw new Error("useAuth must be used within <AuthProvider>");
+  return ctx;
+}