feat(frontend): 认证体系 + 类型定义 + API 服务层

认证:
- AuthContext + useAuth (JWT token 持久化, 登录/登出)
- AdminLoginPage (登录表单, 对接 POST /auth/login)
- axios 拦截器自动注入 Authorization header
- 401 自动清除 token 并跳转登录页

类型:
- api.ts: TASK_STATUS 常量, TaskResponse/ProductScanResponse 扩展字段
- admin.ts: ProductResponse 扩展 + MaterialOption/BomItem

API 服务:
- authApi: login() + getMe()
- materialApi: fetchMaterialGroups() + fetchMaterialItems()
- printApi: getLabelPreview() + executePrint() + getPrinterConfig()
- antd 6.5.3 依赖

字体: simhei.ttf (标签打印用)

frontend/src/contexts/AuthContext.tsx

@@ -0,0 +1,122 @@
+import {
+  createContext,
+  useContext,
+  useState,
+  useCallback,
+  useEffect,
+  type ReactNode,
+} from "react";
+import { login as loginApi, getMe } from "../services/authApi";
+
+// ============================================================
+// 类型
+// ============================================================
+
+export interface UserInfo {
+  id: string;
+  username: string;
+  display_name: string;
+  role: string;
+}
+
+interface AuthState {
+  user: UserInfo | null;
+  token: string | null;
+  loading: boolean; // 初始化时检查 token
+}
+
+interface AuthContextValue extends AuthState {
+  login: (username: string, password: string) => Promise<void>;
+  logout: () => void;
+  isAuthenticated: boolean;
+}
+
+// ============================================================
+// Token 存储 key
+// ============================================================
+
+const TOKEN_KEY = "track_admin_token";
+const USER_KEY = "track_admin_user";
+
+// ============================================================
+// Context
+// ============================================================
+
+const AuthContext = createContext<AuthContextValue | null>(null);
+
+export function useAuth() {
+  const ctx = useContext(AuthContext);
+  if (!ctx) throw new Error("useAuth 必须在 AuthProvider 内使用");
+  return ctx;
+}
+
+// ============================================================
+// Provider
+// ============================================================
+
+export function AuthProvider({ children }: { children: ReactNode }) {
+  const [state, setState] = useState<AuthState>({
+    user: null,
+    token: null,
+    loading: true,
+  });
+
+  // 初始化：从 localStorage 恢复 token
+  useEffect(() => {
+    const savedToken = localStorage.getItem(TOKEN_KEY);
+    const savedUser = localStorage.getItem(USER_KEY);
+    if (savedToken && savedUser) {
+      try {
+        const user = JSON.parse(savedUser) as UserInfo;
+        setState({ user, token: savedToken, loading: false });
+        // 可选：后端验证 token 是否仍有效
+        getMe(savedToken)
+          .then((fresh) => {
+            setState((prev) => ({ ...prev, user: fresh }));
+            localStorage.setItem(USER_KEY, JSON.stringify(fresh));
+          })
+          .catch(() => {
+            // token 过期，清除
+            logoutInternal();
+          });
+      } catch {
+        logoutInternal();
+      }
+    } else {
+      setState((prev) => ({ ...prev, loading: false }));
+    }
+  }, []);
+
+  function logoutInternal() {
+    localStorage.removeItem(TOKEN_KEY);
+    localStorage.removeItem(USER_KEY);
+    setState({ user: null, token: null, loading: false });
+  }
+
+  const login = useCallback(async (username: string, password: string) => {
+    const result = await loginApi(username, password);
+    const token = result.access_token;
+    const user: UserInfo = result.user;
+
+    localStorage.setItem(TOKEN_KEY, token);
+    localStorage.setItem(USER_KEY, JSON.stringify(user));
+    setState({ user, token, loading: false });
+  }, []);
+
+  const logout = useCallback(() => {
+    logoutInternal();
+  }, []);
+
+  return (
+    <AuthContext.Provider
+      value={{
+        ...state,
+        login,
+        logout,
+        isAuthenticated: !!state.token && !!state.user,
+      }}
+    >
+      {children}
+    </AuthContext.Provider>
+  );
+}