add user management system

frontend/src/store/authStore.ts

@@ -0,0 +1,32 @@
+import { create } from 'zustand';
+
+export interface User {
+  id: number;
+  username: string;
+  email: string;
+  is_admin: boolean;
+}
+
+interface AuthState {
+  user: User | null;
+  token: string | null;
+  isAuthenticated: boolean;
+  login: (user: User, token: string) => void;
+  logout: () => void;
+}
+
+export const useAuthStore = create<AuthState>((set) => ({
+  user: JSON.parse(localStorage.getItem('user') || 'null'),
+  token: localStorage.getItem('token'),
+  isAuthenticated: !!localStorage.getItem('token'),
+  login: (user, token) => {
+    localStorage.setItem('user', JSON.stringify(user));
+    localStorage.setItem('token', token);
+    set({ user, token, isAuthenticated: true });
+  },
+  logout: () => {
+    localStorage.removeItem('user');
+    localStorage.removeItem('token');
+    set({ user: null, token: null, isAuthenticated: false });
+  },
+}));