调整系统后台服务器状态检测接口，网站状态检测功能完成

bookshelfplus-frontend/views/component/footer.html

@@ -16,7 +16,7 @@
     // refer: https://www.cnblogs.com/yzeng/p/8268731.html
     function getPageText() {
         var str = document.documentElement.innerText;
-        str += "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; // 数字和英文全部包含进去
+        str += "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; // 数字和英文全部包含进去，避免因为部分数字或字母造成大量生成字体
         var res = [].filter.call(str, (s, i, o) => o.indexOf(s) == i).sort().join('').trim();
         return res;
     }

bookshelfplus-frontend/views/status.html

@@ -37,7 +37,8 @@
                 </div>
                 <div>
                     <h3 class="title">网络后台状态</h3>
-                    <span id="backendStatus" class="info"></span>
+                    后台服务器：<span id="backendStatus" class="info"></span><br>
+                    前台服务器：<span id="frontendStatus" class="info"></span>
                 </div>
                 <div>
                     <h3 class="title">网络数据库状态</h3>