set backend and version env

src/Common.js

@@ -15,7 +15,7 @@ import renderMd from './Markdown';
 
 export { format_time, Time, TitleLine };
 
-export const API_BASE = '/_api/v1';
+export const API_BASE = `${process.env.REACT_APP_BACKEND || '/'}_api/v1`;
 
 // https://stackoverflow.com/questions/3446170/escape-string-for-use-in-javascript-regex
 function escape_regex(string) {

src/infrastructure/widgets.js

@@ -82,7 +82,9 @@ class LoginPopupSelf extends Component {
             <b>通过第三方验证登陆新T树洞</b>
           </p>
           <p>
-            <a href="/_login?p=cs" target="_blank">
+            <a href={(process.env.REACT_APP_BACKEND || '/') + "_login?p=cs"} target="_blank"
+              referrerPolicy="origin"
+            >
               <span className="icon icon-login" />
               &nbsp;闭社
             </a>