优化移动端样式 (#1967)

#### What this PR does / why we need it?

#### Summary of your change

#### Please indicate you've done the following:

- [ ] Made sure tests are passing and test coverage is added if needed.
- [ ] Made sure commit message follow the rule of [Conventional Commits specification](https://www.conventionalcommits.org/).
- [ ] Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

frontend/src/layout/index.vue

@@ -148,7 +148,7 @@ onMounted(() => {
     top: 0;
     bottom: 0;
     left: 0;
-    z-index: 1001;
+    z-index: 9999;
     overflow: hidden;
 }
 

frontend/src/styles/common.scss

@@ -181,7 +181,7 @@ html {
 
 .mask-prompt {
     position: absolute;
-    z-index: 9999;
+    z-index: 9998;
     top: 220px;
     left: 45%;
     transform: translate(-50%, -50%);

frontend/src/views/app-store/apps/index.vue

@@ -119,7 +119,6 @@
                     v-model:page-size="paginationConfig.pageSize"
                     v-bind="paginationConfig"
                     @change="search(req)"
-                    :page-sizes="[30, 60, 90]"
                     :layout="mobile ? 'total, prev, pager, next' : 'total, sizes, prev, pager, next, jumper'"
                 />
             </div>
@@ -259,14 +258,14 @@ onMounted(() => {
         }
 
         .app-desc {
-            margin-top: 5px;
+            margin-top: 8px;
             overflow: hidden;
             display: -webkit-box;
             -webkit-line-clamp: 2;
             -webkit-box-orient: vertical;
 
             text-overflow: ellipsis;
-            height: 45px;
+            height: 43px;
 
             .desc {
                 font-size: 14px;