Revert "fix: Remove pointless Maintenance and Announcement apps (#35852)"

This reverts commit 9274852f2d.

cms/static/sass/views/_maintenance.scss

@@ -0,0 +1,104 @@
+.maintenance-header {
+  text-align: center;
+  margin-top: 50px;
+
+  h2 {
+    margin-bottom: 10px;
+  }
+}
+
+.maintenance-content {
+  padding: 3rem 0;
+
+  .maintenance-list {
+    max-width: 1280px;
+    margin: 0 auto;
+
+    .view-list-container {
+      padding: 10px 15px;
+      background-color: #fff;
+      border-bottom: 1px solid #ddd;
+
+      &:hover {
+        background-color: #fafafa;
+      }
+
+      .view-name {
+        display: inline-block;
+        width: 20%;
+        float: left;
+      }
+
+      .view-desc {
+        display: inline-block;
+        width: 80%;
+        font-size: 15px;
+      }
+    }
+  }
+
+  .maintenance-form {
+    width: 60%;
+    margin: auto;
+
+    .result-list {
+      height: calc(100vh - 200px);
+      overflow: auto;
+    }
+
+    .result {
+      box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.2);
+      margin-top: 15px;
+      padding: 15px 30px;
+      background: #f9f9f9;
+    }
+
+    li {
+      font-size: 13px;
+      line-height: 9px;
+    }
+
+    .actions {
+      text-align: right;
+    }
+
+    .field-radio div {
+      display: inline-block;
+      margin-right: 10px;
+    }
+
+    div.error {
+      color: #f00;
+      margin-top: 10px;
+      font-size: 13px;
+    }
+
+    div.head-output {
+      font-size: 13px;
+      margin-bottom: 10px;
+    }
+
+    div.main-output {
+      color: #0a0;
+      font-size: 15px;
+    }
+  }
+
+  .announcement-container {
+    width: 100%;
+    text-align: center;
+
+    .announcement-item {
+      display: inline-block;
+      max-width: 300px;
+      min-width: 300px;
+      margin: 15px;
+
+      .announcement-content {
+        background-color: $body-bg;
+        text-align: center;
+        padding: 22px 33px;
+      }
+    }
+  }
+}