Theme switch support (#3568)

### What problem does this PR solve?
- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>
Co-authored-by: Jin Hai <haijin.chn@gmail.com>

web/src/pages/login/index.less

@@ -2,10 +2,12 @@
 
 .loginPage {
   display: flex;
+  background-color: rgba(255, 255, 255, 0.1);
+
   .loginLeft {
     // width: 610px;
     width: 40%;
-    background-color: #fff;
+    background-color: rgba(255, 255, 255, 0.1);
     height: 100vh;
     display: flex;
     align-items: center;
@@ -39,7 +41,6 @@
       z-index: -1;
     }
     .white {
-      color: #fff;
     }
     .pink {
       color: #e9d7fe;
@@ -87,15 +88,12 @@
     span {
       font-size: 16px;
       line-height: 24px;
-
-      color: #000000a6;
     }
   }
 
   @media screen and (max-width: 957px) {
     .loginLeft {
       width: 100%;
-      background-color: #fff;
       height: 100%;
     }