Fixes #3606

[loadingspace]

What's the purpose of this PR

用来解决portal未启用auth并且配置了context-path后导致的, 访问首页部分资源加载404问题

Which issue(s) this PR fixes:

Fixes #3606

Brief changelog

1. portal - app.html 中 lodash.min.js 引用路径修改
2. index.html 中 加入获取prefixPath逻辑

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[nobodyiam]

How about we use the same code as that in login.html?

    <script type="application/javascript">
        $(function () {
            $.get("prefix-path", function (result) {
                window.localStorage.setItem("prefixPath", result);
            });
        });
    </script>

[loadingspace]

异步会有加载先后顺序问题，导致prefix-path还未获取，就已经开始加载需要前缀的资源了，从而引起了404问题

[nobodyiam]

那login.html中的这段代码是否也要做同样的修改?

    <script type="application/javascript">
        $(function () {
            $.get("prefix-path", function (result) {
                window.localStorage.setItem("prefixPath", result);
            });
        });
    </script>

[loadingspace]

测试了一下，的确也有上述异步加载问题（会导致zh-CN.json文件404）。又补充提交了 login.html 的修改

[nobodyiam]

LGTM