Factor out post-login splash screen to a new component (#12103)

* Factor out post-login splash screen to a new component

* Move CSS classes to per-component file

* Rename CSS classes

... to reflect the component that uses them

* code review

res/css/structures/auth/_LoginSplashView.pcss

@@ -0,0 +1,34 @@
+/*
+Copyright 2015-2024 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+.mx_LoginSplashView_splashButtons {
+    text-align: center;
+    width: 100%;
+    position: absolute;
+    bottom: 30px;
+}
+
+.mx_LoginSplashView_syncError {
+    color: $accent-fg-color;
+    background-color: #df2a8b; /* Only used here */
+    border-radius: 5px;
+    display: table;
+    padding: 30px;
+    position: absolute;
+    top: 100px;
+    left: 50%;
+    transform: translateX(-50%);
+}