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/pages/admin/AdminLoginPage.tsx

@@ -0,0 +1,99 @@
+import { useState } from "react";
+import { useNavigate, Navigate } from "react-router-dom";
+import { QrCode, Loader2 } from "lucide-react";
+import { useAuth } from "../../contexts/AuthContext";
+
+export default function AdminLoginPage() {
+  const { login, isAuthenticated } = useAuth();
+  const navigate = useNavigate();
+
+  const [username, setUsername] = useState("");
+  const [password, setPassword] = useState("");
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  // 已登录 → 直接跳转
+  if (isAuthenticated) {
+    return <Navigate to="/admin/dashboard" replace />;
+  }
+
+  async function handleSubmit(e: React.FormEvent) {
+    e.preventDefault();
+    if (!username.trim() || !password.trim()) return;
+
+    setLoading(true);
+    setError(null);
+
+    try {
+      await login(username.trim(), password);
+      navigate("/admin/dashboard", { replace: true });
+    } catch (err: any) {
+      setError(err?.message ?? "登录失败，请检查用户名和密码");
+    } finally {
+      setLoading(false);
+    }
+  }
+
+  return (
+    <div className="flex min-h-screen items-center justify-center bg-gray-50">
+      <div className="w-full max-w-sm rounded-xl bg-white p-8 shadow-lg">
+        {/* Logo */}
+        <div className="mb-6 flex flex-col items-center">
+          <div className="flex h-12 w-12 items-center justify-center rounded-xl bg-blue-600">
+            <QrCode className="h-6 w-6 text-white" />
+          </div>
+          <h1 className="mt-3 text-lg font-bold text-gray-800">
+            生产流转 · 管理端
+          </h1>
+          <p className="mt-1 text-sm text-gray-500">请使用工号登录</p>
+        </div>
+
+        {/* 错误 */}
+        {error && (
+          <div className="mb-4 rounded-lg border border-red-200 bg-red-50 px-3 py-2 text-sm text-red-600">
+            {error}
+          </div>
+        )}
+
+        {/* 表单 */}
+        <form onSubmit={handleSubmit} className="space-y-4">
+          <div>
+            <label className="mb-1 block text-sm font-medium text-gray-600">
+              用户名
+            </label>
+            <input
+              type="text"
+              value={username}
+              onChange={(e) => setUsername(e.target.value)}
+              placeholder="如 IRIS 或工号"
+              className="w-full rounded-lg border border-gray-200 px-3 py-2.5 text-sm focus:border-blue-400 focus:outline-none focus:ring-2 focus:ring-blue-100"
+              autoFocus
+            />
+          </div>
+
+          <div>
+            <label className="mb-1 block text-sm font-medium text-gray-600">
+              密码
+            </label>
+            <input
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              placeholder="输入密码"
+              className="w-full rounded-lg border border-gray-200 px-3 py-2.5 text-sm focus:border-blue-400 focus:outline-none focus:ring-2 focus:ring-blue-100"
+            />
+          </div>
+
+          <button
+            type="submit"
+            disabled={loading || !username.trim() || !password.trim()}
+            className="flex w-full items-center justify-center gap-2 rounded-lg bg-blue-600 py-2.5 text-sm font-medium text-white transition-colors hover:bg-blue-700 disabled:opacity-50"
+          >
+            {loading && <Loader2 className="h-4 w-4 animate-spin" />}
+            登录
+          </button>
+        </form>
+      </div>
+    </div>
+  );
+}