feat: 实现用户认证上下文，重构相关组件以支持用户状态管理

web/src/contexts/auth-context.tsx

@@ -0,0 +1,38 @@
+"use client";
+
+import React, { createContext, useContext, useState, useMemo } from "react";
+import type { User } from "@/models/user";
+import { userLogout } from "@/api/user";
+
+type AuthContextValue = {
+  user: User | null;
+  setUser: (u: User | null) => void;
+  logout: () => void;
+};
+
+const AuthContext = createContext<AuthContextValue | undefined>(undefined);
+
+export function AuthProvider({
+  children,
+  initialUser = null,
+}: {
+  children: React.ReactNode;
+  initialUser?: User | null;
+}) {
+  const [user, setUser] = useState<User | null>(initialUser);
+
+  const logout = async () => {
+    setUser(null);
+    await userLogout();
+  };
+  const value = useMemo(() => ({ user, setUser, logout }), [user]);
+  return <AuthContext.Provider value={value}>{children}</AuthContext.Provider>;
+}
+
+export function useAuth() {
+  const ctx = useContext(AuthContext);
+  if (!ctx) {
+    throw new Error("useAuth must be used within an AuthProvider");
+  }
+  return ctx;
+}